Optimizing Dedicated Server using nginx, mysql to handle huge traffic

So, I've website which receives huge traffic regularly, therefor eI use nginx, since it can handle more simultaneous requests. But my website started loading quite slowly and top command on linux bash shows that 584% is in usage ( i have 6 processors on my DS). So your job would be checking nginx, php, mysql settings and seeing if there is possibilities to optimize settings to handle huge traffic better. If you found something. then i would pay you. I would give you server acces via SSH.