Does the owner of an internet café bear the sins of internet users who use it for undesirable things, given his prior knowledge and his guidance to them through advice? And must he abandon this work?

The fundamental principle regarding the teaching of computer science and internet knowledge is permissibility, unless it is known that someone will use what they learn for forbidden purposes. In such a case, it is not permissible to teach them, because that would be cooperation in sin and aggression. Allah Almighty says: "And do not cooperate in sin and aggression."