Building a first person persona is not difficult to do - especially if you base it upon yourself as much as you can.  Read as much about the era as possible.  Put yourself in "their shoes" and act accordingly.

Name.  If do not have a traditional German name, look to yourancestors, if not there, then perhaps you could adopt the name of one ofthe veterans of the unit.

Age. How old are you?  When wre you born?  Well, in thiscase, take you own actual age, subtract it from, say, 1917, and that givesyou your birthdate.   From this, you can determine when you wentto school, what military draft class you were in, what local, nationaland world events you may have experienced, etc.

This is just a start.  You can, and most likely will, spendmany hours pursuing details that really flesh your persona out.  Forsome people, it is one of the most interesting things we do.  To helpstart you out, try this form.