Is a student's fasting acceptable if he is studying in a non-Muslim country and mixes with and shakes hands with women, knowing that the saleswomen and dormitory cleaners are women?

The Prophet, peace and blessings be upon him, described the state of some people in their fasting by saying: "Perhaps a fasting person gets nothing from his fast except hunger and thirst," because the purpose of fasting is to achieve piety. If the fast does not achieve its intended purpose, which is piety, then nothing remains for the fasting person except hunger and thirst.

As for the validity of the fast, the preponderant opinion is that it is sufficient even with the presence of sins, as long as it is not accompanied by the emission of semen.

If you are permitted to reside in a disbelieving country out of necessity, or due to the Muslims' need for your specialization, then beware of the tribulations of those lands, and be extremely careful about your religion. Your discussions with the professor or others should be limited to what is necessary, without expansion, and lower your gaze as much as possible. Know that the permissibility of your remaining in these lands is conditioned upon your not fearing falling into forbidden acts. If you fear it, then you must leave those lands.