How can I combine pagination and filtering in php?

I would like to display some products from database and use pagination as well as checkboxes for filtering. My pagination is working fine. And when I click checkboxes and press "submit," I do get filtered results on the first page. However, when I move to the second or any other page, the checkboxes automatically become unchecked and the filtering gets lost. Here is my HTML code:

<form action="" method="get">
  <input type="checkbox" name="brand[]" value="iPhone">iPhone<br>
  <input type="checkbox" name="brand[]" value="iPad">iPad<br>
  <input type="checkbox" name="brand[]" value="Samsung">Samsung<br>
  <input type="checkbox" name="brand[]" value="Huawei">Huawei<br>

  <input type="submit" name="submit" value="Submit">
</form>

<?php include 'display_products.php';?>

In order to apply filtering I use an IF statement:

if (isset($_GET['brand'])) {
  $filter = implode('","',$_GET['brand']);
  $sql='SELECT * FROM products WHERE brand IN ("' . $filter . '") LIMIT ' . $this_page_first_result . ',' .  $results_per_page;
  $result = mysqli_query($conn, $sql);

  while($row = $result->fetch_assoc()) {
    echo '<div><h3>' . $row['title'] . '</h3><img src="' . $row['image'] . '"<h4>' . $row['price']. '</h4></div>';
  }
} //else display all products from the table of the database

I assume that when I go to the next page, my checkboxes get unchecked, this $_GET['brand'] becomes empty and the "else" statement is activated. I tried to find solutions for this problem, but some of them were not effective and some were too hard for me to understand (I am a beginner). Could you please explain in simple terms how to keep the checkboxes checked and how to keep the filtering throughout all the pages? I saw such ideas as "use session" or "keep the data in url," but I can't figure out how to implement it. So if you are more specific, I would be super grateful. Thank you very much!