Need to configure VPS (CentOs 7) ISP (to Optimize server performance, work security)

A VPS with an ISP on Board and Park sites.
Sorry, already subjected to a third break-in in six months and follow-up, type of fill, web shells, hacking and other nuances of security. In the end, the objectives are two:
1. Configure security VPS-Ki. Specific details of what needs to be done, I unfortunately do not know. It is necessary to coordinate together. Perhaps a ban on write files, execute scripts, function php, a ban on the entry in the database. This is only speculation. The main objective is safety.
2. Speed and optimization. Here, overall, no complaints, but, once engaged in UPU-hell, you want and speed optimize. Similarly, all negotiable. Maybe transition with FastCgi php on nginx, maybe some suggestions – again, I do not understand, we need to discuss. Perhaps to upgrade to CentOs or something.

Budget is flexible and negotiable. If you need a safe deal.