You are not the only one having this issue. AMD has for a long time had issues with this game and I don't know why it is yet to be fixed. Then they came out with Navi and it is even a bigger issue on the new architecture. Crazy to me as this games requirements are pretty low and utilizes an engine that has been around for over a decade and is one of the most popular games on the planet.
There are numerous people if you search the threads with things they say may help. You might try to do that.
I would report the ongoing issue to AMD, driver development is not here in the USER TO USER forums.
Contact AMD:https://www.amd.com/en/support/contact-email-form
This thread from the Steam Forum lists a lot of things to try that you may find useful: Steam Community :: Guide :: CS:GO optimization guide for MOST stable FPS [2019]