"The bus starts from the place where many people are waiting."
Translation:A busz onnan indul, ahol sok ember vár.
Not in Hungarian, no. In English, you can kind of omit part of the comparison, or blend it into the second clause. So, "the place" can be omitted from the above sentence.
In Hungarian, you can't really do that. So, "onnan..... , ahol..... " stays in the sentence.
And "ahonnan" means "from which place". It does not fit with "people".