Complex sentence: In the early days the Ahmadi-ism painted and presnted itself as a the sect of Islam, knowing that they did not fulfill the conditions of being Muslims, especially in believing that Prophet Muhammad (pbuh) is the last and final massenger of Allah.
Split into simpler sentences: In the early days the Ahmadis painted and presnted themselves as belonging to just another sect of Islam, clearly knowing that they did not fulfill the conditions of being Muslims. Ahmadis did not believe that Prophet Muhammad (pbuh) is the last and final massenger of Allah.