If the letter A has become Q and vice versa, it is probably an inversion linked to the switching of the keyboard from QWERTY mode (French keyboard) to QWERTY mode (American keyboard).
Windows 10 no longer works properly? Have you started a repair of Windows 10 but nothing has changed? Now want to start a deep cleaning? So reinstalling Windows 10 is surely the ideal solution to start on a good basis and find a new PC.
Since Microsoft wanted all computers to be compatible with Windows 10, you may find that your computer performed better with your old Windows. This is often the case with people who migrated from Windows 7 to Windows 10.