Reduce Server Load - MYSQL

Website has become very busy in recent weeks. As a result, Server Load is very high from time to time and causing the website to respond very slowly, making my visitors to leave the site because of this issue. I spoke with my Hosting about the Server Load issue. My Hosting say: We have checked the sever for certain period of time and it seems the database is taking too much load, please try to optimize database queries using the help of a developer, which will reduce a considerable amount of load . I'm in a need of help to fix this issue. I require someone with knowledge of PHP and MySQL, to check my Server to optimize the code to reduce High Server Load. Server Specification Hybrid Servers 8-Core Intel Xeon CPUs 2048 GB RAM 100 Mbps Port Speed