If this is a project to learn PHP and MySQL (and maybe Javascript) you should not build it using bootstrap (you've lose all the fun ;). But this is only my opinion.
Also, make sure to filter your user input to avoid XSS attacks. I just posted a story and your page will print HTML and JS verbatim, meaning I could do malicious things. See here: https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)
Apart from that, looks pretty good, well done :)
I will definitely look further into it! Thanks again