Fix 'Error establishing a database connection', increase PHP memory limit, and fix 'file is empty' error when uploading media, in wordpress website WITHOUT Cpanel.

Fix 'Error establishing a database connection', increase PHP memory limit, and fix 'file is empty' error when uploading media, in wordpress website WITHOUT Cpanel.

Warning : Website contains some adult images.

More details:

Which method of access do you have to the server? SSH
What operating system is the server running? Linux
Have you recently made any changes to the website or server configuration? No changes made