Warm up the Y and Z positions
The named German reference is QWERTZ. If you normally use QWERTY, familiar movements for Y and Z can produce the opposite result. Confirm the active layout with a short word before starting a timed test.
A German language setting and a German keyboard layout are separate choices on many devices. You can also enter German through another capable layout. In that case, choose a matching guide or System / other, and keep the built-in converter off.
Use the displayed spelling
The first drill asks for ä, ö, and ü, not ae, oe, and ue. Those alternative spellings can be useful in other contexts, but they do not reproduce this exercise. The second drill includes ß in Straße and groß; ss is likewise a different target sequence.
Focus on the umlaut key before attempting long compounds. When a word goes wrong, compare its beginning and ending separately. A long word can conceal a single omitted letter even when all the special characters are correct.