How insert, update and delete in mysql database in wordpress

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I tried to update and delete database in wordpress by using wordpress query, but it's not working.I also try ajax for data updating and deleting but it's not working. I provide all code in below section

What I have tried:

this code represents table which I get through database and
update and delete query, if anyone knows what I did wrong, please help me

<?php
 /* 
  * Template Name: Show Form Template Page
  */
?>

 <div class="container">
	<div class="row">
		<div class="col-md-12">
			<form method="POST">
			<table border="1">
				<tr>
				<th>Id</th>
				<th>Name</th>
				<th>Email</th>
				<th>Gender</th>
				<th>Age</th>
				<th>Edit</th>
				<th>Delete</th>
				</tr> 


				<?php

				global $wpdb;
				$table= 'wp_contact_form';
				$result = $wpdb->get_results ( "SELECT * FROM $table" );

				if(!empty($result)){

				foreach ( $result as $print ) {   //here $result is an array
													// $print variable is for current row		
 		?>
				<tr>
				<td><?php echo $print->id;?></td>
				<td><?php echo $print->names;?></td>
				<td><?php echo $print->emails;?></td>
				<td><?php echo $print->gender;?></td>
				<td><?php echo $print->age;?></td>
				<td><input type="submit" value="Edit" name="update"></td>
				<td><input type="submit" value="Delete" name="delete"></td>
				</tr>
				<?php
				}
				} 
				?>
		</table>
		</form>
				<?php
				
				global $wpdb;
				$id= $print->id;
				$table= 'wp_contact_form';
				if (isset($_POST['update'])) {
				    $data =array(
				    		'names' => $_POST['yourname'],
				            'emails'    => $_POST['customer_email'],
				            'gender' => $_POST['customer_gender'],
				            'age' => $_POST['customer_age']
				        		);
				    $wherecondition=array(
				    				'id'=>$id
				    			);
				$wpdb->update($table, $data, $wherecondition);
	// $wpdb->update('table_name', array('id'=>'1', 'name'=>'parvez', array('id' => '2')));


			}	
				

				if (isset($_POST['delete'])) {
					// echo "gg";
					// die;
				    $wpdb::delete($table, $wherecondition);

				    }
				    ?>