Is the payment of financial compensation by students to doctors, in exchange for the continuation of lectures in which they specialize in exam questions, considered a suspicion of bribery that falls upon them if they accept it?

There is no objection to your continuing the lectures and bearing the compensations if the professors perform them in their private time, and it does not interfere with their official work, and the questions you receive, beyond those given to other students, do not conflict with the institute's regulations, and no corruption results from it. If any of these conditions are not met, then it is not permissible.