How to speed up a wordpress site?

Question

Server optimization

Terrible site loading speed (with a normal dedicated server)
What working tools can be?
The main loading of the site at the first stage:
- server response time (time until the first byte is received)
If tested on other sites and access to the server, the response is very fast.

Answer 1

If the brakes are on the server side, then the Query Monitor plugin will help. In it you can see queries to the database, their execution time, repeated queries, which plugins make them, which styles and scripts are loaded and what loads them...