It's a non starter really. Susanne is right, Pete Best was simply mistaken. Paul MacCartney spoke a little German onstage the one time I saw him - and it came over as very charming. However, anyone who has heard the Beatles sing "Komm Gib Mir Deine Hand" or "Sie Lieb Dich" is unlikely to be under any illusions that the Beatles were fluent German speakers. The Scouse accents alone made them into near comedy records!