My Breed Is My Puppy?

I adopted Nina from a shelter and was told she was a Shepherd mix. She was rescued from Mexico without any parents so I do not have much of an idea what breed she really is. When we got her at 12 weeks she was 9 pounds. Her last check up about a month ago at 5 months old she was 20 pounds. She is a very good and well behaved puppy. She is shy around other people, but very friendly and playful with my boyfriend and myself. She is so smart and we love her no matter what just wondering what kind of breed she is and how big she will get!

By Brittany