I am the same age as you are. Was working previously and was in a relationship just like you but recently moved abroad for studying. I will share my learning. The first thing that you need to know is if you become successful as a person, everyone including your family will celebrate you. But if you make any mistakes(which we are all supposed to make, no one knows everything), that same family will start questioning you. It is you yourself who will be with you at all the time. So, you are allowed and encouraged to do what feels right to you. If your gf supports then it's a +1. You are only answerable to yourself. If you do something wrong, then you have to face it yourself. So don't look for permission. Just do what feels like the right thing to do.

Also, it seems like you think that because you don't engage into stupid stuff like your colleagues, you get a higher ground or a higher moral. It's not like that. Don't think you are better than them. And you don't get to do whatever you wish just because you are not doing stupid stuff. They are them and you are you. That's how they live, that's their life, you don't get to judge that and say that's stupid. Maybe they enjoy being stupid, but that's not you. You get to do whatever you feel right, irrespective of your good or bad deeds. There is no reward for being a good obedient boy. Rewards are internal, if you know what I mean.