First is this drawing to scale?
If so, I agree it's too crowded and moving the sofa would help. You can hang window treatments to reduce the glare on the tv, but I'm not sure why you would worry about rain....does the window leak? If so, that needs to get fixed.

If it's not to scale then you need to make one that is...get yourself a measuring tape and use it. It will prevent you from getting other oversized furniture for your space. In the drawing above, the dining table looks huge and it looks like there's no way to get by it to get into the apartment.

As far as color and inspiration, go to houzz.com and look for rooms whose color and style you like...that will give you a direction.

Yes you can paint furniture and people do it all the time.

Your sofa:

If your floor is indeed like the herringbone pattern you linked to: I think it's great and would try to keep it. It looks lovely with a European style, e.g Scandinavian or French or Dutch....

[Eclectic Living Room[(https://www.houzz.com/photos/eclectic-living-room-ideas-phbr1-bp~t_718~s_2104) by Amsterdam Media & Bloggers

Here is a link that might be useful: French floors

It looks like moving the couch to the window wall will block the traffic from the bedrooms.
If there is room, I would try the couch forward of the window wall and perpendicular to the wall with the bookcase so that it acts as one side of a "hall" from the bedrooms to the kitchen. Possibly use the buffet piece, or bookcase if it's low, behind the sofa. Place the chair in a right angle to one side of the sofa.

Another arrangement would be to place the couch on the wall shared with your bedroom, TV and storage on the long wall, chairs across from couch. Computer to the left of the window before kitchen entrance. This will give you breathing room between lounge area and dining area. I'd put the tv on the buffet from the dining area until the right piece came along.
Something like this arrangement is what you would see when walking down the entry hall. Imagine that fireplace as the tv.

[Contemporary Living Room[(https://www.houzz.com/photos/contemporary-living-room-ideas-phbr1-bp~t_718~s_2103) by Durham Interior Designers & Decorators Heather Garrett Design

For a small place, getting rid of the little pieces and using fewer large pieces will help with that cramped feeling. The little things by the bufffet can go. Put the tv on a long, low-ish piece of furniture that can hold equipment, movies, etc. Eventually, turning that long wall from the entry into a storage/media center will help reduce that cluttered feeling. You can consider a set or collect pieces that play well with each other.

Get a smaller, but useful dining table. One that expands would be ideal so that you have options if you need length.

While you say the sofa is large, that dining table looks really big for the space. Do you use it much? As a dining table or as a desk or craft space or something else?

Because I'd be tempted to replace the dining table with a rectangular table, and butt the table up to the back of the sofa. It could then be a place to put drinks and remotes while watching TV. And it would stop taking up half the floor space in a small room. You could always move it out from the sofa when you have a dinner party.

Or you could put the table on the window wall, right up against the wall. Then float the sofa in the middle of the room, with its back to the window wall. Then the TV goes on the wall opposite the window. If you are worried about glare on the TV set from the sun, get room-darking blinds or shades.

As for the TV--don't let the wire stop you from putting the TV where you need it. If it is just a longer cable that you need, you can buy the cable in just about any electronics store. Or you can ask your cable company to come and move the cable outlet. My cable company charges $50 to $150 to do this, depending on if you want the cable fished through the walls or not.