Got to post age your age man, forum rules.
I grew up playing in bands (still do) and going to shows 2-3x a week so I'll throw you a few pointers.
A. It's called a "show". Old folks and parents call it a "concert"...
B. There will likely be a mosh pit, which varies but is usually towards the front. Stand a few layers of people behind the pit so that you and your girl aren't jostled around too much. You can stand at the front, by the stage, but usually people are getting jostled around and squeezed in so much that it's less than ideal if you've got a girl with you.
C. Speaking of having a girl with you, shows are a great place for kino. Keep her in front of you so that you can monitor and make sure some idiots aren't going to fly into her full bore from out of nowhere. Use touch to direct her to where she should be or move her when people are moving, etc. People will be moving back and forth as a crowd, sometimes rather unexpectedly and with force, so shield her from the maddening crowd with your shoulders and arms.
D. Are you a Green Day fan? If not you'd do well to learn the words to as many as their songs as you can. It's more fun when you can sing along and you'll appear more authentic and not like some poseur just there for the girl he's with. In addition, look up the opening bands too and if you like them familiarize yourself with their material too.
E. It will be loud. Very loud. A trick I always use is to grab some tp from the bathroom, wad it up into a small ball, and shove it in your ears for makeshift ear plugs. You could bring real ear plugs of course but that seems kind of dorky to me for some reason ha. Plus you can show her the way and look like you do this all the time in the process.
F. When they leave the stage at the end of show, stick around. They'll most likely come back out for an encore. You'll notice most will be still hanging around, that's why.
G. This applies to indoor venues: regardless of how cold it is outside, leave your jacket in the car and encourage her to do the same. It'll get damn hot in there and you don't want to be carrying your jacket the whole time. Also leave your wallet and phone, you don't want to lose them or get jacked. People get pick pocketed at shows all the time. Only bring your ID and cash (for drinks or whatever) in your front jeans pocket.
Alright man, that's about it, good luck!