Hi Krix
Welcome to the board of awesomeness
For your birthday go to your personal view "Persönlicher Bereich" in the main navigation in the black and click on it. In the left navigation you will find a link called Profile, click it. Now, just add your day of birth at the bottom in the dropdown. Save it and you will be fine.
In the Topic "Events" are events and upcoming events. The teams are made depending on the type of gaming mostly you will stand with your team but if you are alone as a singelplayer you will be randomly put into a team. If you have time for an event you would like to join and you don't have a gun yet, maybe you should ask in the eventsection it self if someone is that handsome to lent/rent you his equipment.
what you should bring to an airsoftgame is definitly good shoes (hiking shoes for example), trausers who could get dirty and damaged, as well some tshirts, and some clots to change after the match. At least you need a portion of fun, excitement, adrenalin, pleasure a.s.o ^^