Is masturbation forbidden or permissible with the left hand? And is it permissible to talk to girls at university about ordinary matters such, as studies?

Masturbation is forbidden in any form whatsoever. Speaking with girls at university is an evil and great trial, for the Prophet, peace and blessings be upon him, said: "I have not left behind me any trial more harmful to men than women," and he also said: "Beware of the world and beware of women, for the first trial of the Children of Israel was concerning women." If a male student is compelled to speak with a girl out of necessity, he should limit himself to the extent of that necessity, while adhering to the Sharia (definition) guidelines, such as avoiding private seclusion (khalwa (definition)), not speaking in a soft or alluring manner (khudoo' bil-qawl), and lowering the gaze.