>> How can I adjust Hackers keyboard that at first, directly the corresponding german umlaute ä ö ü appear? <<
Not sure if you are asking about defaults or behavior, but I'm
guessing you might not be aware of the general android osk keyboard
design philosophy.
On most, if not all, android onscreen keyboards, a <longtap> brings up
one or more options.
Since most keyboard configurations do not show the 5th numeric row, it
is assumed that the user normally wants to type a number, so,
<longtap> on the top row defaults to the corresponding number on the
row above... i.e. "o" "defaults" to "9"
However, if you <taphold> the "o" a full selection of accent options
appear, and you simply slide your finger to the desired character and
when you "release" your finger that character is typed.
You noticed the different behavior of "a" for example, since it is a
vowel, but not on the top row, so, it does not "default" to a number.
On the hacker's keyboard, if you use settings to "turn on" the number
key row, you will then notice that <taphold> vowels on the 4th row no
longer default to numbers.
An important point to understand is that tapping a key does nothing...
the character is typed only when you _remove_ your finger from the
keyboard. For example, you can <taphold> the "j" key, then slide to
the "h" key and when you release, an "h" will be typed rather than a
"j"
This behavior is exploited on many keys other than the top row... for
example, <taphold> the punctuation keys and see what is available.
The hackers keyboard uses this capability extensively... for example
<taphold> the "l" and "n" keys.
You might also revisit other keyboards such as the default google
keyboard and compare and tinker with what they offer on many available
<taphold> keys.
Hope that this information is helpful,
Beverly Howard