How do I show my dog that he did something wrong ?!?

You correct him the instant he did it. Dogs do not understand delayed punishment (or rewards)

You have to catch him in the act. After the fact will not work. Like showing a dog his poop after he has pooped, you have to catch him in the act. or getting into the garbage, showing him the mess all over the room, doesn't work.

After the fact does not work.

You can't show a dog anything. You have to catch him in the process of being "bad" and reprimand him with a loud NO.

Ignore it when he does something wrong and go over the top with praise when he pleases you.

You catch him in the act and scold him with your voice- firm tone, no yelling. tell him to lay down somewhere and make him watch you clean the mess up.

As already said, correcting a dog after the event will normally mean he just hears you being annoyed, not why. A dog might look guilty, but he's just reacting to your body language. It really must all be about prevention and avoidance with dogs.