You partially think language, and partially in other senses. You can think in smell, sounds, touches, tastes, and obviously imagery. Your actual thoughts though, are sentences, or at least words. I think both in English and Dutch. I used to try to only think in English, to practise it even further, but now it’s just a habit.

Thinking goes way faster than speaking. Thinking is a monologue. You can think faster than you can talk, without anyone interrupting you. You can think in sounds your mouth can’t even replicate.