Disclaimer: Information here is not official in any way and we encourage you to search for the original sources. There may be no original sources sometimes.
To calculate how much travel expenses you have accumulated for the tax declarations:
http://www.imacc.de/lohnabrechnunggehaltsabrechnung/lhstberechnung/pendlerpauschale/index.html
Which things can be considered profesional expenses:
How much did you pay in a year of taxes:
http://www.imacc.de/lohnabrechnunggehaltsabrechnung/lhstberechnung/lohnsteuerrechner/index.html
This is in the case that you live in Garching bei Muenchen. Take you passport to run all this errands.
This explains almost everything.