Book recommendations for CompSci related math
I am not only searching for a book, but also an approach of how to learn matc without pain on my own.


If you learn best from and/or enjoy a good lecture, your best bet is probably the MIT open courseware lectures. They have Calculus, multiple versions of Linear Algebra 


  I am still going to "Gymnasium", the german counterpart to the high school


Unsurprising, MIT open courseware also has an excellent collection of canonical CS courses that will be helpful for gaining background in CS theory for the high schooler. I worked through the Structure and Interpretation lectures my Junior year of high school, and that was definitely worth the time. There is also an Introduction to Algorithms course.

Of course, there is also a course on exactly what you want -- Math for CS -- but there are no video lectures.

See here: http://ocw.mit.edu/courses/#electrical-engineering-and-computer-science