I have two questions one what happened if a girl misses her period for the first time and another question i have is can a girl get pregnant if you sucked her pussy?

You can not get a girl pregnant by sucking her pussy. Menstrual irregularities are not uncommon. If the girl had sex since her last period, she should do a home pregnancy test at 4-5 days past the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully.

Women can miss their period for a number of reasons including severe weight loss, hormonal imbalances, and pregnancy. You'll need actual intercourse for conception to occur.