Dogs can open doors

Dog opens doors

can someone give me a tip on how I can stop my dog ​​from opening doors?

We have 2 dogs.
Ben + # 8211; meanwhile over 8 months old + # 8211; unfortunately has a big weakness for it.
Just recently I was in the shower, it makes a hell of a blow and who is standing in front of me: Ben, who has opened the bathroom door.
Yesterday my father was here with his dog. When the two left, Ben followed them on the stairs. I heard my father say, Ben, you can't go with me, go back to your seat. Then he's out the door. A few seconds later I heard a knock. Immediately down the stairs, the front door was wide open and Ben was walking around the courtyard. He came straight away and I scolded him and sent him to his seat.
But since it was too dangerous for me if I'm in the office (2nd floor) etc. I locked the front door yesterday at noon so that the guy wouldn't start such an action again.
Towards evening a friend came, she rang the bell and who is the first to stand at the door and try to open the door: Ben !! (But luckily it was still locked, otherwise he would have opened the door in front of me)

Then I let him sit down before I unlocked the door. That worked. Could that have something to do with the rowdy phase, because at the moment he is sometimes unbearable + # 8211; also across from Dongo?
By obnoxious, I mean that he behaves like a big puke to other dogs when he's alone again breaking things (he managed to kill a fringed carpet within 1 hour), etc.