The init sequence for HD44780 is:
Wait more than 15 ms after power up
Write 30h, wait over 4.1 ms
Write 30h, wait over 100 us
Write 30h, wait over 40 us
Write 38h, wait 40 us
Write 08h, wait 40 us (display OFF)
Write 01h, wait 40 us (display ON)
Write 06h, wait 40 us (Entry mode set)

After the 3rd write the Busy Flag can be used instead of a fixed delay period.

Cannot read German, what is your clock speed?

Hal