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Hi,
what I actualy want to do is to builld a circuit which operates an engine in two different direction (due to the operator choice) and for a specific period of time.
So I need to know two things:
What can I use to change the direction of the flow (something like switch)?
How do I make it stop after let's say 10 sec (automaticly)?

thnks for any help!

Most of your questions are answered in this thread:
https://www.electro-tech-online.com/threads/motor-reversal.21952/

When you say engine, you mean an electric motor right? Not a a gas engine? You can use an H-bridge for changing current direction in an electric motor. YOu can use timer circuits or microcontrollers to make it stop after 10s. A lot of it is in the linked thread.