Thank you very much for getting in touch. Memrise is, at the moment, a tool for learning vocabulary rather than grammar. The intention is to help you to drive forward with the main memory-intensive part of language learning, which is where we can give you most help. I hope that makes sense; perhaps some of the other community members can recommend it to you.
Like Ben said Memrise is just for vocabulary at the moment. I'd recommend looking picking up a book or using http://german.about.com/ for grammar. Of course memorisers are always here to help explain something if you run into trouble. Viel Glück und Erfolg! :)