Hello Polac. (:
Here’s how to fix your mouse:
Try booting into safe mode, to boot into safe mode press F8 on your keyboard while your pc is booting.
Try disconnecting and reconnecting the mouse. You could also try a different USB port for the mouse.
If it’s a wireless mouse, try replacing the batteries.
Try reinstalling the mouse drivers, to do this go to Control Panel > Device Manager. From there you should see a listing for your mouse. After selecting your mouse, you should have the option to remove the driver. Once the driver has been removed, reboot the machine.
Take your mouse to a repair centre.
Hope this helps. (: