Is one who studies in Europe sinful if he looks at women in class without fear of temptation or for a discussion session, or is forced to attend a mandatory music class, or misses Friday prayer due to work and his inability to go to the mosque?

Studying in schools that contain great evils is not permissible due to the danger it poses to one's religion, unless there is an extreme need for it. In such a case, it is permissible to continue studying there while fearing Allah by lowering your gaze and avoiding unnecessary discussions with girls, only engaging to the extent of necessity. You should also try to convince the administration to allow you to attend Friday prayers and to be excused from music classes.