Sorry, hiding what? The shape of the room? Not sure that's possible.

Does the bed fit where the wardrobe currently is? If so, I might move it there and change the door swing so it swings out into the hallway, or put in a pocket door instead.

This is pretty common in apartment buildings. What do you want to hide?

I would want a more open balcony, but unfortunately you can't change the architecture of the building!

I was thinking of making a furniture over the bed headboard which might be parallel with the front wall. maybe it will create a more regular room shape. Is it a good idea?

Embrace the shape it's kind of cool. I cannot think of a piece of anything hung on the wall that will make the shape feel any different

You use bedroom just for sleeping, why you want it to " hide"?

I think your bedroom is an interesting shape. Unique. As PCC, said, embrace it. It IS cool.

It is an apartment building, so the OP can't just "design away the problem". This is quite common in high rise apartments when they slice up the space into individual apartments.