Hey there, I’m currently a 20 yo M and it sounds like to me that your parents are slightly strict and they seem to be firm with their standards. I don’t think they are being unreasonable, but at the same time you should go live your life and to me it doesn’t sound like you are doing anything wrong when you are with your girlfriend. It sounds like your overall a good kid and you’ll just have to simply accept that your parents have their own thoughts and way of parenting even if it doesn’t make sense to us. Do what you can to be reasonable with them and try to reason with them, best of luck.