When I first apply pressure it lags and doesn't work properly on Krita. I have a windows 7.
I'm sorry, but... * Windows 7 isn't supported * You're not giving any unseful information whatsoever about your problem. Please read https://docs.krita.org/en/untranslatable_pages/reporting_bugs.html if you want to learn how to make a useful bug report * And problems with tablets are always driver issues * And you should check whether you have enabled the stabilizer in the freehand tool options, since that delays the stroke until you get out of the stabilizer radius.