German
German uses separate words for numbers up to twelve, which can all stay the same in seximal.
0: null
1: eins
2: zwei
3: drei
4: vier
5: fünf
10: sechs
11: sieben
12: acht
13: neun
14: zehn
15: elf
20: zwölf
in German, the ones place is spoken before the tens place, with the word "und" (and) separating them. (with no spaces, obviously, because this is German we're talking about here)
21: einundzwölf
22: zweiundzwölf
23: dreiundzwölf
24: vierundzwölf
25: fünfundzwölf
multiples of ten are formed with a -zig suffix, which can be adapted into an analogous -sechs suffix for multiples of six.
30: dreißechs
40: viersechs
50: fünfsechs
the word "nif" can be loaned into German, and can be combined with other words the same way German uses "hundert".
100: nif
101: nifeins
110: nifsechs
200: zweinif
1000: sechsnif
5555: fünfundfünfsechsniffünfundfünfsechs
the -exian series needs a little bit of adapting to work the same way as how German deals with -illions, because in German, it's "one Million" (capital M) and "two Millions".
1 0000: eine Unexian
2 0000: zwei Unexianen
1 0000 0000: eine Biexian