Slowness and saturated Ram following transition to Win 11

I have a Dell G5 15 5587 (2019) laptop - (16go Ram - SSD 256 + DD 1To - Intel 6c/12t CPU - GPU 1060 6go)
 
Since switching to Win 11 last November (voluntary automatic migration), I have had major problems with slowness.
The RAM is quickly saturated at more than 85%, everything reacts very slowly, after an hour I have to restart the PC to regain some flexibility).
Documents take a good minute to open, with more than 5 PDFs the reader crashes, etc.
It's a real hassle.
The CPU is never used much (I don't play on it anymore), but it takes crazy hits which can last 30sc where it gets carried away before returning to a normal office level.
 
Do you have any suggestions? Thanks in advance.