So in the start of my file i am get the Id of my product, so i can differ between products and store data correctly. Thats my php:
<?php 
if(isset($_GET['dish_did']))
{
    //get food id
    $dish_did = $_GET['dish_did'];
    //get data
    $sql = "SELECT * FROM dish WHERE did=$dish_did";
    //execute
    $res = mysqli_query($link, $sql);
    //count rows
    $count = mysqli_num_rows($res);
    //check whether the data is available or not
    if($count==1)
    {
        //we have data 
        //get from database
        $row = mysqli_fetch_assoc($res);
        $nom = $row['nom'];
        $description = $row['description'];
        $last_rating = $row['last_rating'];
        }
    else{
        //not availible
        header("location: error.php");
    }
}
else{
    header("location: rate.php");
}    
?>
After some HTML i have the following POST. I use this to save the data entered by the user in an other table (different table than dish).
<?php
//check whether submit clicked
if(isset($_POST['submit']))
{
    //get all details
    $dish_id = $_POST['dish.did'];
    $review_date = date("Y-m-d h:i:sa"); //Rating Date
    $user_review = $_POST['RatingLong'];
    //save in database
    //Create SQL to save data
    $sql2 = "INSERT INTO review SET
    user_review = '$user_review',
    review_date = '$review_date',
    dish_id = '$dish_id'
    ";
    //Execute the Query
    $res2 = mysqli_query($link, $sql2);
    //check wether query executed successfully or not
    if($res2==true)
    {
        //Query Executed and Review Saved
        $_SESSION['review'] = "<div class='success'>Review Successfull.</div>";
        // header('location:'.SITEURL);
    }
    else{
        //Failed to save review
        $_SESSION['review'] = "<div class='success'>Error.</div>";
        // header('location:'.SITEURL.'about.php');
    }
}
?>
Without the dish_id i am able to store data, but they aren´t assigned (so useless).
I am not sure how i can link the id correct, to be saved. I have seperate links for every product by id: http://localhost/Project/index.php?dish_did=2  for example.
What i have to change, that user_review and review_date is stored correctly with the same dish_id (table review) as dish_did (table dish).
ADDITIONAL QUESTION:
how can i comment ?
edit:
added rate.php code and database
<?php
                $sql = "SELECT * FROM dish WHERE hide ='1'";
                $res = mysqli_query($link, $sql);
                $count = mysqli_num_rows($res);
                if($count>0)
                {
                    echo'<div class="row">';
                    while($row=mysqli_fetch_assoc($res))
                    {
                        $did = $row['did'];
                        $nom = $row['nom'];
                        $description = $row['description'];
                        $last_rating = $row['last_rating'];
                        
                    ?>
                    <div class="mb-4"></div>
                            <!-- <div class="row"> -->
                            <div class="col-md-3">
                                <div class="thumbnail">
                                    <a href="index.php">
                                        <img src="img/gallery/01.jpg" class="rounded-top">
                                    </a>
                                    <h4 class="text-center my-3"><?php echo $nom; ?></h4>
                                    <p class="text-center"><?php echo $description; ?></p>
                                    <a href="<?php echo SITEURL; ?>index.php?dish_did=<?php echo $did; ?>" class="btn btn-success" role="button">Jetzt Bewerten!</a>
                                <!-- </div> -->
                            </div>
                            </div>
                            <?php
                    }
                
                }
                else{
                    echo "<div class='error'>Food not available.</div>";
                }
                ?>
Here my database:
create table users
(
uid int primary key AUTO_INCREMENT,
username varchar(25),
password varchar(25),
created_at date,
score int
);
create table dish
(
did int primary key AUTO_INCREMENT,
nom varchar(25),
description varchar(250),
last_rating int,
hide int DEFAULT 0 NOT NULL
);
create table review
(
review_id int primary key AUTO_INCREMENT,
user_id int ,
dish_id int ,
user_rating int ,
user_reveiw varchar(100),
review_date datetime,
foreign key (user_id) references users(uid),
foreign key (dish_id) references dish(did)
);
