Tashahhud Duaa
The only essential part to be recites in Arabic in the prayer is Surah Fatiha and the adjacent part from the Qur’an. The rest is the azkaar are not prescribed, but some of them were recommended and suggested when asked by the sahabah, including durood. These are very good duas which teach the manner to supplicate. However, one can supplicate in one’s own language. The same goes for the Friday sermon. It should be in the local language. Saying ‘peace be on you o prophet’ is not shirk. Shirk means when someone associate a partner with God. These word have been kept intact as a tradition, not that one believes that he is assessing the prophet.