Is a person sinful for sitting in a place where people are being backbited, due to his need for internet, even though he has forbidden the evil but they did not respond, and he is preoccupied with his religious questions, not with their talk?

If you object to those who backbite and you need to remain in their presence while trying to avoid listening, then there is no sin upon you for what reaches your ears of their speech, as there is a difference between intentionally listening (istima') and unintentionally hearing (sama'). According to Ibn Taymiyyah, whoever hears disbelief, lies, backbiting, or singing unintentionally, like someone passing by on a road and hearing it, is not sinful by the agreement of Muslims. However, whoever sits and listens to that without disavowing it with his heart, tongue, or hand, is sinful by the agreement of Muslims, citing His (Allah’s) saying: {And when you see those who engage in [offensive] discourse concerning Our verses, then turn away from them until they enter into another conversation. And if Satan should cause you to forget, then do not remain after the recollection with the wrongdoing people. And those who fear Allah are not held accountable for them for anything, but [it is] a reminder that perhaps they will fear Allah.}