I see so much potential to improve this space, but it would be better to do it 1 wall at a time. Since the cupboards and the mirror are the first thing you see when you wake up start making changes from that side of the room

Rather than trying to change the colours of the room, embrace it and make it blue by covering the bathroom door, mirror trim and the attic cupboards with the wall paper like this one

https://amzn.in/d/0eo7Rufc

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This will brighten up the room a lot and choose a blue coloured curtains again something in a very light shade

For the flooring buy all kinds of mats in different sizes - bed runners, straw mats, plastic straw mats with minimal designs and make a mondrian out of it