Ubuntu Server Troubleshooting for Website

I have my own server with Ubuntu where I host my website. I've been running into some error messages that are affecting my website's performance. I'm unsure of the exact nature of the problem and would appreciate someone with experience troubleshooting Ubuntu servers and website hosting issues.

An ideal freelancer for this project would:
- Have extensive experience with Ubuntu server management
- Be able to quickly diagnose and solve hosting issues
- Provide clear communication about the problem and the solution