Translation of einlösen

Let's not forget how we started. We were writing each other very long messages and today we are both much more fluent in both languages. No book could have brought us that far. Cheers.
I've been working on and off on the dictionary during the entire week, and I'll spend some more hours on it this coming weekend. Sometimes he would get a bit mixed up and use formal Castilian sometimes instead of informal.
I have a lot of fun while learning. Which one do you like better, Spanish or German? Last year I learn approximately 18 months Spanish as a second language, but then we had to leave the course.