HI Klauss,
Look for web resources on the 109s - there shoudl be many sites that have line drawings showing the panel lines, or up close photos of warbirds might help. Also, take a look at books such as Osprey's Me109 Aces of the xxxxxxxxx Series.
I wouldn't let missing a few panel lines stop me from continuing to work on a skin - you will learn a lot by digging in, and you will eventually develop a library of resources to use. You will eventually discover somewhere what those missing panel lines look like (go into the game and zoom in externally on a good skinner's 109 and pan around it). In the meantime, there is plenty learn about weathering, scratches, dirt, stains, etc.
Good Luck.