Hey guys,

Please, help! I am a beginner in German, my level is about A1+. I know that in German you frequently transform articles, for instanse, an + dem = am, etc. Most of these transformations are very common, but recently I came upon "hinterm, hintern, unterm, untern, vorm, aufm", and so on. Is this correct? Are they usable? How common are they among native German speakers?

Thanks a lot!