phpMyAdmin and Net2FTP upload_max_filesize settings

I have an Ubuntu 24.04.2 LTS server with ISPConfig Version: 3.3.0p1. and many websites installed. I'm trying to change the phpMyAdmin upload_max_filesize settings but I can't find how or where I can do that. Besides, I'm trying to set up Net2FTP as a file manager but I get HTTP ERROR 500 and I don't know if it's a PHP version issue. Any clues? Is there a better option for managing files?