How can I make the opening look OK?

[klippor]

My extension on the house has a "flat roof." Sloping towards the middle from both sides.

I want to enlarge the opening to the max in the room with the flat roof, all the way up to the tongue and groove ceiling. The problem then becomes the other side of the wall, the one with the gray wallpaper. The ceiling slopes from left to right in the first image. Roughly 1.75cm lower at the far right of the opening.

Does anyone have any tips on how I should do it to make it look OK from both sides?

 

[Bronken]

I think I understand what you mean, but why this change?
I mean, what will be better? Is it too low, ugly?
Maybe it helps to come up with ideas?

 

[klippor]

It's too low! I don't often hit my head anymore, but it happens!

 

[Bronken]

If the beadboard ceiling (1st picture) is slightly slanted, it will probably be very difficult to make it "harmonious".
I (not exactly a master carpenter) would just increase the door hole height but with the same design:

 

[klippor]

Yes, it feels difficult. I guess I'll have to live with it being quite noticeable.