"This is my teacher Mohamed."
Translation:هٰذا مُعَلِّمي مُحَمَّد.
not really, not needed ... unless you want to emphasize the speech ... you can add هو then
some text book introduce such way of teaching to approximate the idea of the verb (to be) to the non-Arab learners ... because Arabic does not use (to be) in forming sentences like English and many other European languages do. Thus, the solution to that gap and to match the grammar scale for such languages, some books would presume adding the pronoun in the place of "is" - while truth is.. it's not really necessary .... but it can be added to add force and emphasis in the sentence (Turkish and I think Russian behave the same at some point)