VPS Linux server and wordpress issues

I'm having performance issues with my VPS Linux server and WordPress. Specifically, I've been experiencing intermittent errors on certain domains within it. I haven't yet tried to find solutions for the problem myself, and I'm looking for help to get my system up and running smoothly. The current state of my server is that it's partially functioning, but I'm having difficulties with errors on some domains. If you're experienced with VPS Linux Servers and WordPress and can help me address the performance issues I'm having, please reach out.