Arduino Nano pins are always high
i solved my problem. After the comment from idfka I realised that the pins of the nano boards are manufacturer specific. My board is this one: https://www.google.de/search?q=arduino+nano+pins&amp;client=firefox-b&amp;dcr=0&amp;tbm=isch&amp;source=iu&amp;ictx=1&amp;fir=g5a8iQQg303lcM%253A%252Ctmj5jJzH5Ig2qM%252C_&amp;usg=__72_pjW6IJT1IOYTAo5yM4-X_zkA%3D&amp;sa=X&amp;ved=0ahUKEwiIlKX7hbLaAhXBJVAKHWHxC_EQ9QEILjAB#imgrc=uEf4hxPbfX8vZM:

Before that i used the numbers for the pins from this one: 
https://www.google.de/search?q=arduino+nano+pins&amp;client=firefox-b&amp;dcr=0&amp;source=lnms&amp;tbm=isch&amp;sa=X&amp;ved=0ahUKEwiIlKX7hbLaAhXBJVAKHWHxC_EQ_AUICygC&amp;biw=1920&amp;bih=954#imgrc=AJV5mxdwaZYG6M:

And this is from idkfa:
http://www.pighixxx.com/test/pinouts/boards/nano.pdf

I never thought that different manufacuters will use different pins.

#define TASTE_HOCH 14       //A0
#define TASTE_RECHTS 17     //A3
#define TASTE_UNTEN 16      //A2
#define TASTE_LINKS 15      //A1


The change of the numbers solved my problem.