I have put a tablet with oh on the wall like control center of OH.
It is connected with wifi socket.
I would like to turn off the chrger when i leave the home and turn on when i come back.
So with charger is clear how to turn it off/on.
But with android system, how can i turn off the screen and lock it and again unlock?
You can send commands (and soon updates) from Tasker to openHAB. There is no built in way to get data from openHAB into Tasker yet (if ever) so you would have to use the openHAB REST API.