Here are some links for learning German.
Lingolia helps you to learn and practice german vocabulary and grammar in an easy way. There are many tests to check your skills. If you have any problems, look at the site help.
SCHUBERT- Verlag, Leipzig
Online-tasks for learning german as a foreign language with lots of trainings for beginners and advanced pupils.
Here are some links for learning Mathematics.
Mathematics for pupils and teachers. All subjects are covered with lots of trainings and tasks.