What does deveras con tigo mean in Spanish?

Without the complete context of the phrase, it's a little difficult to translate.

The best I can give you is "Really? With you?"

De veras, is a phrase that means "Really"

Contigo is a the Word that means "with you".

With the sentences before that phrase, it could possibly take on another context, but with the information provided, that's about the closest translation that you can get.