Hi Teo Pavel
Nice to know that you are interested. I myself will also apply for google summer of code pro gramme with sympy.
I tell you the resources which will elp you to get started with you application and project proposal.
First of all visit this
https://github.com/sympy/sympy/wiki/Development-workflowThis tells you how the development works in SymPy.
Then you can go to this link:
https://github.com/sympy/sympy/issues?state=openThis will tell you about some of the issues/bugs/enhancements required/proposed in SymPy.
They can also be sorted with tags like Geometry, Easy to Fix etc.
Go through them and try to find one which matches your skill set and interest. Try to fix one of them.
And then send a Pull Request. The moderators will comment on your code and will guide you to get the stuff merged.
Hope this helps.
Feel free to ask anything on the forum. Community is really supportive :)
Cheers
Anurag