I added a new translation for German personal (de_du). In Germany we are using two different ways to address people. The formal way is to address people with "Sie". The personal (informal) way is to meet people with "du".
I took the strings from local_moodlemobileapp.php in the german package (de) and I changed all strings where you can read the formal address "Sie". I uploaded the changed file for the second german package (de_du) so we will have both versions for the next release of the mobile app.