This happens to me as well. After 4 nights the fps drops to single digits even though I had 40 fps before. This is apparently caused by some non-game related update (Windows, methinks).
There was an earlier post on this if you can find it. Dev response was something like "we did not cause this".

Two things you can do:
1) Use Vulkan launcher to launch the game from Steam. However, it can crash the game while you are playing so that's the risk but it apparently gets rid of the low fps.

2) Log out after every single match. Your first few nights will be smooth and then it will get single digit fps again. So this is far from a solution.
BUT if you do not log out after every game, I find that the game will have single digit fps from day 1 itself. Even worse.

Originally posted by YaBoyRandy:

shoulda got the 1080 dog

I have a Laptop dog,

Originally posted by YaBoyRandy:

shoulda got the 1080 dog

Try to understand that it is not related to how powerful a graphics card is. I used to get smooth fps until the end of the match. Now it's smooth only for a few nights before dropping to single digit FPS.

Shocking

Or just try the thing i do , turn on vsync apply , turn it off ,apply . Works for me everytime my fps drops

Well I got the new 399.07 Graphic Drivers. Windows is all up to date. DirectX version still doesnt work. Tried Vulcan and it is FIXED. How do I make the game start with Vulcan as Default?

I'm NOT sure, but try this: Right click game in steam library>Properties>Set Launch Options>Add this: