Urgent help with site speed and performance

Hi,

I tried to change speed and performance according to https://premium.wpmudev.org/blog/increase-memory-limit/
but nothing works and all my small settings remain. Nothing works: .htaccess, wp-config, php.ini or whm
I am frustated and site is so slow. Please help. Access is granted and if you need other details to login let me know.

Michael