I’m fairly new using PHP for my website project can’t tell what’s wrong. Maybe by the mix of HTML and PHP scripts? https://pastebin.com/7PKh6n1h
There are several problems with your code. First and foremost, you are using dangerous, obsolete code that has been completely removed from Php. You need to use PDO with prepared statements. https://phpdelusions.net/pdo
You also need to learn about separation of concerns. You have Php, HTML, and CSS all mashed together. If you used a proper IDE with syntax highlighting your noob problems would be very obvious.
Whatever “tutorial” you copied that code from, toss it along with this code. It is not fixable. Study the PDO tutorial I linked to and re-write the code properly. If you still have problems, then come back and we will help you.