Optimization of site

There was a problem with the load speed and the load on the server.
In the individual browsers, the site lasts up to 3 seconds.
Increase the speed of the site in 3 times
Reduce the volume of data uploaded 2.5 times
Double rating of the site in the eyes of Google tools
+ correctly and thinly adjusted cache (it was enabled but not adjusted)
+ Images optimized
+ Optimized code