"We are tall and pretty."
Translation:Wir sind groß und schön.
I don't quite understand the question. Do you mean how to say it in German, if you talk of a person to be "big" in German?
That depends. If you really mean the offensive remark that he is fat, it would be "dick" in German. If you mean he is no more a child, you can use "groß" (the same word you use for "tall". Context will make it clear what you mean).