So until now I was practicing lockpicking at Peshek mill in Rattay at the practice chest but the thing stoped locking now it says only open. Any advice where I can practice now?Or how can i make the chest locked again?
There is a door at the mill set to very easy, you find it to the left as you come out of your bedroom. Behind the door is also another easy chest which you can open. Apart from that, your best practice is to just walk around and open every lock you see.
The practice chest will stay permanently open once you have unlocked it a number of times, in my case when i hit level 3 lockpicking.
Also there is a chest within your bedroom set to very easy.
Just go around lockpicking everything, I just scream in my head “No more locked doors!” and proceede to unlock everything. 
Yea already started doing it.Just finished up Rattay LOL