Need assistance on IP.Board website

Please bid only if you're familiiar with Invision Power Board and its apps. I'm looking for someone to help me with several things on one of my webiste powered by IP.Board. 1) Ensure maximum security on the website 2) We've been hacked a week ago. I need to understand how it happened and if the hackers have done anything threatning the security of the website and privacy of the members. 3) Optimize website speed 4) Quick advice on SEO (if possible considering your skillset, this is not mandatory)