Hi Stian,
it´s great to have you here! On our website you find an online-grammar-trainer for free with more than 20.000 questions!
So, when you have learned even a few word and little grammar in german, you can solve many questions with our online-trainer.
If you have never learned german before, it would be best, to learn german step-by-step at home with a good german book or with a teacher.
I hope you enjoy our site,
nice greetings,
Anna