Deathadder V3 (wired)

Synapse 3 or 4?

ı tried 4 and 3.

but the same problem persists.

What app are you using to check the polling rate?

Did you’ve tried the cleanup tool? https://rzr.to/Tf53xj

If this won’t help - I’d try one more thing → go to device manager expand universal serial bus controllers - remove any USB Root hub instance then reboot PC.

I'm using Razer's own application (polling rate tester). But you don't even need the application. Because you can see it with the naked eye.

I haven't tried the other steps yet. I'll get back to you after I've tried them.

After you said that, I tried everything, but it didn't work.

I’d test it on another PC with Synapse. I think it’s an OS related problem, that something is blocking the polling rate.

I use a laptop. Could this be related to that? 

It’s not hardware related. I’d still bet on some windows stuff broken.

So what should I do? How can I be sure there is no problem with the mouse? 

I think I've found the problem. There are three USB ports on the laptop. All three are occupied (headphones, mouse, keyboard). When I remove one, the mouse works fine. Now I don't know how to solve this problem :) Would a hub work?

Hub is NOT an option - it’s just a splitter. Also Razer periperals are selecrive about hubs. Are these 3 ports are at least USB 3.0?

You can also try updating laptop drivers/firmware/bios for all things.

Yes, all of them are 3.0

and everything is up to date

 I have a bloody brand keyboard, and when I remove it, the problem disappears. I don't understand. 

Strange… maybe some motherboard limitation. I’d try updating BIOS for your motherboard and check.

Brother, I really thank you. You really helped me a lot but the BIOS is up to date. I don't think there's much I can do. For now, I'll keep using it by plugging it in and out.