I can install and configure CSF for you, but the issue behind slow/unreachable sites, typically, is server configuration + load.
Relevant Skills and Experience
I run a web hosting service and have extensive server experience.
Proposed Milestones
$5 USD - New employer to Freelancer - Full account setup milestone.
$95 USD - Firewall installed, server tweaked and running stable.
Bid includes Apache/PHP/mysql optimization, which should take care of slow/unreachable issues.