Can a girl still pregnant even if using a condom?

yes it could break
If you use it correctly, and it doesn't break, then she won't get pregnant.
Yes, condoms are only 98% effective; there is still a 2% chance.
Only not having sex will keep a girl from not getting pregnant. Nothing is fool proof. Condom's reduce the chance of a girl getting pregnant. They are not and will never be 100% effective
Yes, unfortunately, the condom is only between 80 and 95 percent effective. That means that in one year of correct condom use, approximately one out of ten women will get pregnant.