PC Security Audit Needed

I'm concerned my personal computer may have been hacked. I've noticed slow performance but haven't installed any new software or updates recently.

I'm looking for someone to:
- Check for signs of unauthorized access
- Analyze and improve system performance
- Ensure all security measures are up to date

Ideal skills and experience:
- Expertise in cybersecurity
- Experience with performance optimization
- Familiarity with various operating systems

Please provide a detailed plan of action and any relevant certifications.