WordPress Performance Optimization & Server Security

I'm currently experiencing crashes with my WordPress site that is hosted on a dedicated server. The site's poor performance has led me to believe that not only is there a need for troubleshooting and optimization, but a potential risk of DDoS attacks or similar malign activities also exists.

Ideally, I'm seeking an expert who can:
- Intensively troubleshoot the site and server for any performance issues,
- Optimize the server and site's overall performance,
- Investigate for any potential security threats like DDoS attacks or hackers.

Preferred skills and qualifications for this job are:
- Profound experience in WordPress troubleshooting,
- Solid understanding and experience with Plesk,
- Extensive knowledge on dedicated server optimization including database optimization, server configuration, and security enhancements.

Your role in this project will be crucial in maintaining and enhancing the performance and security of my WordPress site. If you’re confident that you can deliver on these requirements, then you're the expert I'm looking for. Let's enhance my site's performance and safeguard it from any possible threats.

Seeking ASAP solutions