Use this instead:
Concatenate the html then return it.
function check_my_login( $atts)
{
$html="<form action="" name="" method="post" enctype="multipart/form-data">";
$html .= '<div class="form-group">';
$html .= '<label for="description">Project Description</label>';
$html .= '<textarea name="p_description" placeholder="Project Description" class="form-control">';
if(isset($_POST['p_description']) && $_POST['p_description'] != ''){
$html .= $_POST['p_description'];
}
$html .= '</textarea>';
$html .= '</div>';
$html .= '<div class="form-group">';
$html .= '<label>Project Attachment</label>';
$html .= '<input type="file" name="p_attachment">';
$html .= '</div>';
$html .= '</form>';
return $html;
}
add_shortcode( 'kentaUser', 'check_my_login' );