Thanks,
I suspected the microswitch for forward and reverse then i changed with new microswitch only because the complete pcb board was expensive.
Fault was disappear and okay.

Linde L16 trucks: there were different generations and types, so the serial No would be usefull.
If it's 131 series, as I presume, you have the problem either with the potentiometer or with the microswitches in the tiller head.
You should disassemble the tiller head, and you'll find the pot connected to the printed board, and the row of small switches surrounding the plastic axle.
Check them.
Eventually check the wires around.