Show them article 34 in the children's rights act.
Jk, i don't even know what article 34 states.
Anyway,
If then don't accept you, then make new friends who actually like you for who you are not for some religion.
Religion doesn't make you a person- sure it will teach you morals etc but a good human being should have some common sense morals anyway and shouldn't need to be dictated by an invisible figure.
Also, talking back is good at times- you need to let these people know they are in the wrong and don't just accept everything they say.
If you are going to lose friends in the end anyway, you may as well talk back while you can because they are being racist in a way.
As for the girl, I know it sounds incredibly harsh but if she is a Muslim, then her family is unlikely to approve of you. But I guess, you should keep trying and like someone else said set your beliefs outside and try to get to know her as if religion doesn't exist.
Good luck!