>GUYS! I HAVE A GIRLFRIEND NOW!
Congratulations!
>What should I do?
Stop panicking. Statistics show that more than half world's male population did find themselves in this situation. Some more than once. It's not the end of the world - or your life.
>How should I treat her?
Friendly but respectfully. Don't forget kisses.
>Should I give her lots of presents?
Give her a reasonable amount of presents. Remember - it's not the present that matters, but your feelings towards her behind the present. An interesting thing to try would be buying something without a clear plan - just spontaneous presents when you feel like making a present, instead of just buying something to your anniversary or her birthday. She should never expect something from you to a certain date - it takes surprise and excitement out of act of gifting. But of course you should acknowledge anniversaries, birthdays and other important days - make them special, like having a special evening together - having a fancy date at a restaurant, or walking with her to ballet or philharmonic concert etc.
>Should I marry her right away?
No. Not right away. Try to live with her as roommates for at least half a year, to see if you're compatible in everyday life. (В быту.)
>Should I propose tomorrow?
See the precious point.
>Should we get our parent's approval before we start our wedding?
Yes, that's important.