Usman Asar

Adam, approach is right, BUT, considering your approach it SEEMS to me that you've installed moodle first time using the script installer? softacolous? else you'd be perfectly familier with the installation/up-gradation process.

Anyway, i'll link Rick's videos that will assist you in upgrading moodle with ease.

https://moodle.org/mod/forum/discuss.php?d=401983#p1621924

If your first install was using script installer, I will thoroughly recommend installing from start and import courses in new one as script installed moodles tend to break the code at some point.

Jose, you cannot compare WordPress to Moodle in terms of performance for WordPress comes with 12 database tables in all, whilst moodle comes with 450+, where WordPress is widely used CMS so hosting providers optimize their servers to accommodate WordPress's performance in priority (WSCache, LSCache etc)

if your clean moodle installation is faster compared to your questionable moodle, then it must be the theme or some plug-in making your moodle slower, you can check which one is slowing down your moodle, by installing all plug-ins that you've got originally installed one at a time and see which one is degrading your performance.