You don't use the room as it is
Push all the furniture into the middle and cover with an old bed sheet
Tape double newspaper over the carpet
And do the prep (painting is easy in comparison)
Sort out damp patch, sand, fill, sand, sugar soap, let dry. It will probably take about a week being realistic.
Then paint from top to bottom
Ceiling first, usually easy as it's usually just two new layers on top of white.
I never bother to tape up for ceiling because you go over the walls
Cut in with brush first and the roller away
Then depending on how good you are with a brush, either tape up ceiling edges then paint walls or cut in with the brush freehand. I advise taping in. You might want to do the ceiling first so it will be fully dry whilst you prep walls.
Brand new colour on walls will make such a difference.
Then do woodwork.
It will take 2 weeks max. By end of January you will have a new room.
Listen to lively radio whilst working.
It will feel yours then
A place you want to be in on return to home.
Tackle bookshelves and other stuff once room is ready.
You can always fill and paint a bookshelf for a stop gap.
Lamps, freestanding pointing up and a table reading lamp
Move a speaker in there.
Get TV on wall to create floor space.
But one step at a time, room decorated first and once you have spent time working, dancing and singing along to KissFM (pick your belter station of choice) you will FEEL differently about the space and about yourself for accomplishment of the task.
It's not going to change if you do nothing OP.