German niedrig is a more generally applicable translation of English "low". Tief can cover the meaning of niedrig in many contexts, but not vice versa.
deep (also figuratively)Wie tief ist das Wasser? How deep is the water?Sie hat ein tiefes Verständnis der russischen Kultur. She has a deep understanding of Russian culture.
lowDu hast das Bild zu tief gehängt. You hung the picture too low.