Quite sad to read this. In Germany paid days off are mandatory by law (four weeks per year). Most branches give additional paid days, up to two more weeks. You are required to take the statutory four weeks, usually until end of March the following year. Some employers have less restrictive rules so that you can save vacation days for up to two or three years.

Even for minimally paid jobs and/or short term jobs the same laws apply, and the vacation days will be accumulated.