You do have the option of changing the profile of your tyres, but if you want to improve ride quality then you need a higher profile than the 235/50 your Tiguan is currently using. You could change to a 235/55 or a 235/60 profile which should help the ride quality, but it is worth bearing in mind that this will also affect the handling slightly. A taller profile will mean the sidewall deflects more during hard cornering and the steering response may not be as sharp, but you may feel that this is a worthwhile trade-off for increased ride comfort.