Sigue los enlaces detenidamente
https://hostadvice.com/how-to/how-to-change-common-php-settings-on-ubuntu-18-04/ // Configuracion PHP + MySQL + APACHE
https://stackoverflow.com/questions/44045478/how-do-i-enable-the-dom-extension-in-the-php-ini // dom Extension PHP
https://stackoverflow.com/questions/53705179/can-i-install-gd-library-with-php-7-2 // gd Extension PHP
https://www.digitalocean.com/community/tutorials/how-to-rewrite-urls-with-mod_rewrite-for-apache-on-ubuntu-18-04 // MOD REWRITE
https://www.techrepublic.com/article/how-to-set-change-and-recover-a-mysql-root-password/ // ROOT Mysql
https://linuxize.com/post/how-to-create-mysql-user-accounts-and-grant-privileges/ // Permisos específicos para User + Database Mysql
REINICIAR APACHE: sudo service apache2 restart