Rechter Seitenstreifen auf einer Straße

Because this isn’t a motorway. Speeds are lower, so a parked vehicle isn’t as dangerous. 

If I’m not wrong, you may stop here only if there is a problem like you are not feeling well, car issues, etc.

In Germany, parking is defined as being stopped for more than 3 mins. That’s why you may stop and park here. However the hard shoulder isn’t an actual parking spot.