Hello and good day, for the current occasion one question concerns me. And this is about the following: In addition to my main job I trade online in small style with spare parts and tires, partly also work colleagues buy from me and pick up the parts at home. The whole runs under the small entrepreneur regulation as a side trade. Now a good friend asked me if I could install the sold parts to him, or if I could help him with the installation. the born screwdriver, in addition, he lacks the space or the possibility to do so. I, on the other hand, have learned space and time the profession of the car-mechanic. I have to say, for my own vehicles I have a tire-monger and balancing machine and a small lifting platform at home in the garage (vehicle-specific things I can have in the garage). My question, can I install the sold parts in my spare time for free, so without any consideration or not? Thank you already Once.