Many fonts on Typekit support German. You can browse fonts that support German by selecting "German" from the list of supported languages in the sidebar under browse fonts.
In order to serve fonts in German, you must enable the "all characters" set in your kit. All fonts that support German include (at minimum) the following letter characters:
| A | B | C | D | E | F | G | H |
| I | J | K | L | M | N | O | P |
| Q | R | S | T | U | V | W | X |
| Y | Z | a | b | c | d | e | f |
| g | h | i | j | k | l | m | n |
| o | p | q | r | s | t | u | v |
| w | x | y | z | « | » | Ä | Ö |
| Ü | ß | ä | ö | ü | ‘ | ‚ | “ |
| „ | ‹ |