Dell G3 3579 Overall slow performance / Hard disk at 100%

Hi everyone. First of all, I have a Dell G3 3579 laptop, Intel i5-8300H, 2.30GHZ, 2304 MHZ, with 8GB RAM.

A bit of context: I bought this laptop 3 years ago. During the first year, the performance was excellent. During the second year, with each Windows update, it started to slow down in performance, as well as with the increase of files on the hard drive, but nothing serious. Then I upgraded to Windows 11 (from Windows Update, which recommended me to do so), and that's when my migraine started.

The laptop started to slow down in every way: booting, opening browsers, surfing the internet, opening music files, photos and videos in the file explorer, opening programs (Photoshop and Premiere specifically). I couldn't go back to Windows 10, so I had to format the computer to its factory state.

After that, the performance was better than what I had with Windows 11, but it was worse than what I had before. Every day, for the last six months, I notice a significant decline, so I set about optimizing my laptop.

I followed all the recommendations from Microsoft and Dell and nothing: disable some services, clean cache, clean hard drive files, run chkdsk for errors (I have none), uninstall and reinstall antivirus, disable startup programs, suspend programs in the background, disable notifications, update Windows Update, update drivers through SupportAssist (from the program and from Dell's site), edit energy power plan, optimize and defragment disk, check for malware, I cleaned the laptop fans, in short, I've done everything.

My problem: my laptop is slow in everything. I used to be able to play Genshin Impact and it worked 100%, and now it takes me up to an hour just to open it. I can't use Adobe Premiere anymore, it's impossible. The only thing my laptop is good for now is just to check emails and edit a little in Photoshop. I have the hard disk almost always at 100%, even when I don't have anything open on my laptop. 

I even used PC Manager and AVG TuneUp to "optimize" the performance, but nothing. I have all the updates (Windows 10 22H2) , and my laptop looks like 2010. Right now, with just the browser open, my CPU is at 21%, my ram at 84% and my disk at 100%. I have half the space on my hard drive.

At this point, what can I do?