I've tried soo many ways changing the margin and other things in my css in my code but nothing works. The only thing that i am asking is where should i change the code to make my pictures orientation after I upload from vertical to horizontal.
Here is the code:
function showMyImage(fileInput) {
    var files = fileInput.files;
    for (var i = 0; i < files.length; i++) {           
        var file = files[i];
        var imageType = /image.*/;     
        if (!file.type.match(imageType)) {
            continue;
        }           
        var img=document.createElement("img");
        img.style.width = "20%";
        img.style.marginTop = "10px";
        img.alt = "image";
        img.classList.add("thumbnail");
        var reader = new FileReader();
        reader.onload = (function(aImg) { 
            return function(e) { 
                aImg.src = e.target.result; 
            }; 
        })(img);
        reader.readAsDataURL(file);
        var gallery = document.querySelector(".gallery");
        var div = document.createElement("div");
        div.style.display = "inline-block";
        div.appendChild(img);
        gallery.appendChild(div);
    }    
}
var slider = document.getElementById("myRange");
var output = document.getElementById("demo");
output.innerHTML = slider.value;
slider.oninput = function() {
 output.innerHTML = this.value;
}
const buttonPrintOrSaveDocument = document.querySelector(
    ".button-print-or-save-document"
);
function printOrSave() {
    window.print();
}
buttonPrintOrSaveDocument.addEventListener("click", printOrSave);
label textarea{
        vertical-align: top;i
    }
    div { text-align: left; }
.thumbnail {
    display: block;
    margin-bottom: 10px;
}
.gallery {
  display: flex;
  flex-wrap: wrap;
  margin-top: 10px;
}
.gallery > div {
    margin-right: 10px;
}
.gallery img {
  display: inline-block;
  
  object-fit: cover;
  margin: 5px;
}
.slidecontainer {
  width: 100%;
}
.slider {
  -webkit-appearance: none;
  width: 100%;
  height: 25px;
  background: #d3d3d3;
  outline: none;
  opacity: 0.7;
  -webkit-transition: .2s;
  transition: opacity .2s;
}
.slider:hover {
  opacity: 1;
}
.slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 25px;
  height: 25px;
  background: #04AA6D;
  cursor: pointer;
}
.slider::-moz-range-thumb {
  width: 25px;
  height: 25px;
  background: #04AA6D;
  cursor: pointer;
}
<h1 align="center"> DATABASE </h1>
<h3> <b>Diametri i gypit: </b> </h3>                        
<div class="slidecontainer">
  <input type="range" min="63" max="1800" value="63" class="slider" id="myRange"> 
  <h4 align="left"> fi ɸ : <span id="demo"></span> mm</h4>
</div>
<label for="lang"><b> Materiali Gypit </b> </label>
<select name="Materiali" Id="lang">
  <option value="Azbest">Azbest</option>
  <option value="GRP">GRP</option>
  <option value="Pllastik">Pllastik</option>
  <option value="Heker Cingtun">Heker Cingtun</option>
</select>
<div>
   <p> <b> Anëtarët: </b></p> <textarea rows="5" cols="20"  ></textarea>
</div>
<label>     
<p><label for="w3review" value="Fshati"> <b> Fshati: </b></label></p>
<textarea id="w3review" name="w3review" rows="2" cols="20"> </textarea>
<form action="/action_page.php">
<p><label for="w3review" value="Përshkrimi"> <b> Përshkrimi: </b> </label></p>
<textarea id="w3review" name="w3review" rows="4" cols="80"> </textarea>
<! -- Upload picture --> 
<p> <b> Ngarko foto: </b> </p>
<input type="file" accept="image/*"  onchange="showMyImage(this)" multiple id="gallery-photo-add" />
<br/>
<div class="gallery"></div>
<br/>
<img id="thumbnil"  src="your_image_url" width="300" height="200" alt="image"/>
<br>
<br>
<br>
<br>    
</br>                       
</br>
<button class="button-print-or-save-document">Ruaj</button>
If anyone could help me I'd appreciate that.