const btncalc = document.querySelector('.calcit');
const summetext = document.querySelector('.summe');
const backend = document.querySelector('.backenduser');
const update = document.querySelectorAll('.update');
const backendstk = document.querySelector('.backendanzahl')
const appstk = document.querySelector('.appanzahl')
const preisproapp = document.querySelector('.proapp')
const preisprobackend = document.querySelector('.probackend')
const jährlich = document.querySelector('.rabatt')
update.forEach(input => {
  input.addEventListener('input', function () {
    calcSum();
  })
});
//funktion damit der Slider sich beim eingeben vom input field bewegt
function updateAppUser(val, inputtype) {
  if (inputtype == 'Appuserrangecolor') {
    document.getElementById('AppInput').value = val;
  }
  if (inputtype == 'AppInput') {
    document.getElementById('Appuserrangecolor').value = val;
  }
  calcSum();
}
function updateBackendUser(val, inputtype) {
  if (inputtype == 'Backendrangecolor') {
    document.getElementById('BackendInput').value = val;
  }
  if (inputtype == 'BackendInput') {
    document.getElementById('Backendrangecolor').value = val;
  }
  calcSum();
}
//Rechnung für die Anzahl von Backend und App-Benutzern
function calcSum() {
  var backendanzahl = document.getElementsByClassName("backenduser")[0].value;
  var appanzahl = document.getElementsByClassName("appuser")[0].value;
  var annual = document.getElementById("annual");
  var myList = document.getElementById("myList");
  var backendtype = myList.options[myList.selectedIndex].value;
  var paymenttype = annual.options[annual.selectedIndex].value;
  var percent = 1; //Standardvalue for yearly
  if(paymenttype == "M"){
    percent = 1.1; //standardvalue for monthly
  }
  //Preisstaffelung für app und backend
  apppreis = 7.5;
  backendpreis = 35;
  if (backendtype == "ZR") {
    if (backendanzahl < 5) {
      backendpreis = 35 * percent;
    } else if (backendanzahl < 11) {
      backendpreis = 32.50 * percent;
    } else if (backendanzahl < 21) {
      backendpreis = 30 * percent;
    }
  } 
  if(backendtype == "Z"){
    if (backendanzahl < 6) {
      backendpreis = 20 * percent;
    } else if (backendanzahl < 11) {
      backendpreis = 18 * percent;
    } else if (backendanzahl < 21) {
      backendpreis = 16 * percent;
    }
  }
  if(backendtype == "ZR"){
    if (appanzahl < 11) {
      apppreis = 7.5 * percent;
    } else if (appanzahl < 26) {
      apppreis = 7 * percent;
    } else if (appanzahl < 51) {
      apppreis = 6.50 * percent;
    } else if (appanzahl < 76) {
      apppreis = 6 * percent;
    } else if (appanzahl > 76) {
      apppreis = 5.5 * percent;
    }
  }
    if(backendtype == "Z" ){
      if (appanzahl < 11) {
        apppreis = 7.5 * percent;
      } else if (appanzahl < 26) {
        apppreis = 7 * percent;
      } else if (appanzahl < 51) {
        apppreis = 6.50 * percent;
      } else if (appanzahl < 76) {
        apppreis = 6 * percent;
      } else if (appanzahl > 76) {
        apppreis = 5.5 * percent;
      }
    }
   
  
  if (isNaN(proapp2)) proapp2 = 0.00; //turn NaN intro number
  
  
//Rechnungen für gesamtsumme
  var mytext = (((backendanzahl * backendpreis + +appanzahl * apppreis) * 1)).toFixed(2);
  summetext.textContent = mytext+"€";
//Rechnung für Backendpreissumme
  var backendpreissumme = (backendanzahl * backendpreis).toFixed(2);
  backendstk.textContent = backendpreissumme+"€";
//Rechnung für Apppreissumme
  var apppreissumme = (appanzahl * apppreis).toFixed(2);
  appstk.textContent = apppreissumme+"€";
//Rechnung für Preis pro Backendbenutzer
  var probackend2 = ((backendpreis * backendanzahl) / (backendanzahl)).toFixed(2);
  preisprobackend.textContent = probackend2;
//Rechnung für Preis pro App-Benutzer
  var proapp2 = appanzahl > 0 ? ((apppreis * appanzahl) / (appanzahl)).toFixed(2) : "0.00";
  preisproapp.textContent = proapp2;
  
  if(paymenttype == "J"){
    var jährlicherrabatt = ((backendanzahl * backendpreis + +appanzahl * apppreis)*12).toFixed(2);
    jährlich.textContent = jährlicherrabatt+"€";
  }else if(paymenttype == "M"){
    checkHide();
  }
}
//Rechnung für Jährlich und Monatlich(10% Rabatt für Jährlich)
  function checkHide(){
    var hidden = document.getElementById('hiddenMonthly');
    hidden.style.visibility = 'hidden';
  }
//Funktion für das Verändern der Farbe wenn der Slider bewegt wird
const appUserRangeColor = document.querySelector('#Appuserrangecolor')
Appuserrangecolor.addEventListener('input', function () {
    // (118-50)/(277-50) = 0,26
  // (this.value - this.min) / (this.max - this.min)
  var percent = ((this.value - this.min) / (this.max - this.min))*100;
  const bg = getComputedStyle(this).getPropertyValue('--background');
  const slider = getComputedStyle(this).getPropertyValue('--slider');
  Appuserrangecolor.setAttribute(
      'style',
          ` background:linear-gradient(to right,${slider},${slider} ${percent}%,${bg} ${percent}%) `
  )
})
const backendUserRangeColor = document.querySelector('#Backendrangecolor')
Backendrangecolor.addEventListener('input', function () {
  var percent1 = ((this.value - this.min) / (this.max - this.min))*100;
  const bg = getComputedStyle(this).getPropertyValue('--background');
  const slider = getComputedStyle(this).getPropertyValue('--slider');
  Backendrangecolor.setAttribute(
      'style',
          ` background:linear-gradient(to right,${slider},${slider} ${percent1}%,${bg} ${percent1}%)`
  )
})
const appInput = document.querySelector('#Appuserrangecolor')
AppInput.addEventListener('input', function () {
  const bg = getComputedStyle(this).getPropertyValue('--background');
  const slider = getComputedStyle(this).getPropertyValue('--slider');
  Appuserrangecolor.setAttribute(
      'style',
          ` background:linear-gradient(to right,${slider},${slider} ${this.value}%,${bg} ${this.value}%) `
  )
})
const backendInput = document.querySelector('#Backendrangecolor')
BackendInput.addEventListener('input', function () {
  const bg = getComputedStyle(this).getPropertyValue('--background');
  const slider = getComputedStyle(this).getPropertyValue('--slider');
  Backendrangecolor.setAttribute(
      'style',
          ` background:linear-gradient(to right,${slider},${slider} ${this.value}%,${bg} ${this.value}%)`
  )
})
.grid-container {
    display: grid;
  grid-template-columns:600px 250px ;
  grid-auto-rows: minmax(150px, auto);
  justify-items: stretch;
  align-items: stretch;
}
.grid-item-1 {
  align-self: start;
  justify-self: center;
}
/* Background Styles Only */
@import url('https://fonts.googleapis.com/css?family=Raleway');
* {
  font:13px/20px PTSansRegular,Arial,Helvetica,sans-serif;
}
.text-grey{
  color:grey;
}
header{
  text-align: center;
  font-size: 20px;
}
*, *::before, *::after {
  box-sizing: border-box;
}
html, body {
  background-color: rgb(255, 255, 255);
  height: 100%;
  margin: 0;
}
.grid-container {
  padding: 60px;
  width: 100%;
  grid-template-columns: 250px 200px;
  
}
.td, tr, th{
  font:13px/20px PTSansRegular,Arial,Helvetica,sans-serif;
}
#Backendrangecolor, #Appuserrangecolor {
  --background: rgb(96,125,139,0.33);
  --slider: rgb(17, 166, 7);
  background: var(--background);
  -webkit-appearance: none;
  width: 150px;
}
#BackendInput, #AppInput {
  --background: rgb(96,125,139,0.33);
  --slider: rgb(17, 166, 7);
  background: var(--background);
  -webkit-appearance: none;
  width: 150px;
}
.grid-item {
  font-size: 15px;
  padding: 20px;
  padding-top: 15px;
  background-color: #f8f8f8;
  color: #222;
  border: 7px solid rgba(96,125,139,0.33);
}
.grid-item:nth-child(odd) {
  background-color: #f8f8f8;
}
.target { display: none; }
input[type=range]{
  border-radius: 32px;
  height: 10px;
  cursor: pointer;
}
<html lang="en">
  <head>
    <link rel="stylesheet" href="styles.css">
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
  </head>
  <body>
    <div class="grid-container" >
      <div style="width: 270px"class="grid-item">
        <header>Preiskalkulator</header>
        <div class="slidecontainer">
          App-Benutzer: <br>
          <input id="Appuserrangecolor" value="0" onchange="updateAppUser(this.value);" type="range" min="0" max="100" oninput="Math.abs(this.value); updateAppUser(this.value, 'Appuserrangecolor');" class='appuser update'></input>
          <input style="width: 30px;border-color: var(--form_border_color);" type="text" id="AppInput" value="0" placeholder="1-100" oninput="this.value = this.value > 100 ? 100 : Math.abs(this.value); updateAppUser(this.value, 'AppInput');"><br>
          Backendbenutzer: <br>
          <input id="Backendrangecolor" value="1" onchange="updateBackendUser(this.value);" type="range" min="1" max="15" oninput="this.value = this.value > 15 ? 15 : Math.abs(this.value); updateBackendUser(this.value, 'Backendrangecolor'); " class='backenduser update'></input>
          <input style="width: 30px;border-color: var(--form_border_color);" type="text" id="BackendInput" value="1" placeholder="1-15" oninput="this.value = this.value > 15 ? 15 : Math.abs(this.value,); updateBackendUser(this.value, 'BackendInput');"><br>
        </div>
        <b > choose software </b>
        <select style="width: 150px;" id = "myList" onchange = "calcSum()" >
          <option value="Z">Zeiterfassung</option>
          <option value="ZR"> Zeiterfassung + Rechnungswesen</option>
        </select>
        <select style="width: 150px" id = "annual" onchange = "calcSum();checkHide()" >
          <option onclick="('hidden')" value="J">annual</option>
          <option value="M">monthly</option>
        </select>
      </div>
      <div class="grid-item" style="width: 270px">
        <table style="width:100%;text-align: right;">
          <tr>
            <td style="font:13px/20px PTSansRegular,Arial,Helvetica,sans-serif; width: 138px" >App-Benutzer<br > <div class='text-grey'>pro <span class="proapp" >7,50</span>€</td></div>
            <td style="width: 62px" class='appanzahl'>75,00€</td>
          </tr>
          <tr>
            <td style="font:13px/20px PTSansRegular,Arial,Helvetica,sans-serif">Backend-Benutzer<br ><div class='text-grey'>pro <span class='probackend'>35,00</span>€</div></td>
            <td class='backendanzahl'>175,00€</td>
          </tr>
          <tr><td colspan="2"><hr></td></tr>
          <tr>
          <td >Gesamtpreis mtl.:<br><div class='text-grey'>(zzgl. MwSt)</td></div>
            <td class='summe'>75,00€</td>
          </tr>
          <tr id="hiddenMonthly">
            <td>Total amount<br></td>
            <td class='rabatt'></td>
          </tr>
        </table>
      </div>
      <script src="./app.js"></script>
  </body>
</html>
<!DOCTYPE html>