Instead of scattering good money on guessing what is wrong, you would be better finding someone local to you that has VCDS or Carista, if you can't do that then find an independent VW Group specialist workshop, failing that any SEAT/VW/Skoda/Audi workshop to run diagnostics on that car.
Or you could buy Carista and check what faults are getting logged, don't buy a cheap OBD2 scan tool as it will only check engine emissions codes.