This is only one of the kinds of solutions I can think of/done, but it should help most of you who have keyboard lag or mouse lag or problems with osu after upgrading I hope.
Try changing the compatibility
1. Go to task manager.
2. With Osu open in the background, right click osu on the task manager and click 'Properties'
3. Go to the tab under 'Compatibility'
4. Run the Compatibility Troubleshooter and it should say that Osu! should run at a specific windows version.
5. Click 'Try Recommended Settings'
6. Once it's done, Press on the 'Test the program'.
Done! Osu should be fixed.
However,
In my case, My osu only worked when I pressed 'Test Program' every time I wanted to play osu, otherwise I'd get back the lag
Good luck to anyone who is having problems
Try changing the compatibility
1. Go to task manager.
2. With Osu open in the background, right click osu on the task manager and click 'Properties'
3. Go to the tab under 'Compatibility'
4. Run the Compatibility Troubleshooter and it should say that Osu! should run at a specific windows version.
5. Click 'Try Recommended Settings'
6. Once it's done, Press on the 'Test the program'.
Done! Osu should be fixed.
However,
In my case, My osu only worked when I pressed 'Test Program' every time I wanted to play osu, otherwise I'd get back the lag
Good luck to anyone who is having problems