Can you give me advice for my first time having sex?

Be selective: You know the basics. Hopefully this is somebody decent and that you really like. Bring birth control and barrier protection. Spend a very long time on foreplay, exploring one another's bodies. In fact, you may choose to forego intercourse for a time and enjoy other things instead. When you are ready, you'll know. It will be better than you've been told. Best wishes.