Hi again,
after trying several times, differen USB sticks and so on I had to chose another terminal than the default.
Welcome to pfSense! Please choose the appropriate terminal type for your system. Common console types are: ansi Standard ANSI terminal vt100 VT100 or compatible terminal xterm xterm terminal emulator (or compatible) cons25w cons25w terminal Console type [vt100]: cons25wNo I could run through the installer process