FPS drops after some time in the server

[Draghoone]

GTA V version? Latest
Up to date? Yes
Legit or Pirate copy? Legit
Steam/CD/Social Club? Social Club
Windows version? Windows 10, 1809 build
Did you try to delete caches.xml and try again? Yes
Error screenshot (if any)
System specifications i7 4770 3.4ghz, 16gb ram ddr3 1600mhz and a gtx 1060 6gb
What did you do to get this issue? No clue
What server did you get this issue on? More or less on any server
CitizenFX.log file
.dmp files/report IDs

So basically i started playing FiveM again after 1 year. 1 year ago, i had 8gb ram and no ssd, and the game kept crashing on any rp servers. So i updated the ram and added a ssd, where fivem is now installed.
Now, i can play on servers, but with a fps problem. When i join a server, the fps is “stable”. I mean, i don’t reach the 60 if the server’s has too many resources, but i get 40-50 which is fine for me.
The problem comes after 15-30 minutes that i play on the server, where the game starts to visibly become more laggy and less smooth. I get no small freezes, no stutters, just lower fps (about 15-20).
So the question is, why does this happen? What could it be? I use MSI Afterburner and put the gpu at his maximum % of power, and at the maximum fan speed. The temperature is always log, not going above 65 degrees. Also the usage is at 30-40% (minimum gta settings), the ram is at 50-60% and the cpu at 65-70%.

[system]

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