Lovely sofa - traditional with a modern edge. Will look gorgeous. I think you need to balance traditional with modern but don't be afraid to incorporate the odd special antique piece which will give your rooms a nice ecclectic feel and make them look as though you have collected things over time rather than rushed out & bought them all at once. For example, most entertainment units are pretty uninspiring however if you could find a gorgeous antique cabinet & convert the doors to slide inwards you could end up with a lovely unit that disguises the TV when doors are closed which will also make your small room appear larger. As your rooms are small, if it was me I would keep it simple with clean lines as you have done with your sofa and also soft in tonings. Try to minimise the heaviness in your pieces through legs on cabinets etc. so that they float above the floor. Some ideas in pics below & some shops to visit. Don't rush - take your time & do one room at a time & it will come together beautifully. Choose big pieces first. Good luck!

I'd consider putting the corner sofa and TV stand in the dining room, moving the stand-alone chair and footstool and tall lamp near the stove as a "reading nook" and placing the dining table in the living room, leaving enough for a walkway from the entry to the current dining / possible living room. In terms of the actual furniture, everything other than the colour of the dining chair fabric looks pretty good. I would start by decluttering and removing anything that isn't functional or which you don't find aesthetically pleasing. I'd personally remove the mirror in the bar as I don't think it gels very well, the tiny framed art near the stove, the art on the wall near the TV as it's too small and hung too closely and the drum kit (unless the drum kit is used on a daily basis). I really like the Marimekko print and, IF you like it, then I would use it as inspiration for adding colour to each of the rooms, possibly even a "feature" wall using the bright blue from the print (although I'm not a huge fan of feature walls). A few minor changes may also help, like replacing the blown bulb in the wall sconce, storing the ironing board somewhere else and taking down the "hanging" glasses in the bar area as they're visual clutter right at eye line height.

I think you need a combo of chairs and a couch as the photos make it look like a through fare. black is very heavy so I would soften with a fur throw or similar. Focus on texture in your textiles and cushions. Mustard/ gold can look good against black. If you are changing soft I would go with something withe legs to lighten the look.

Studying your photos, the lounge is sitting in the part of the room that ideally should have a small dining table. This tells you the current lounge is way to big for the space. Your area is the same size as my lounge room. I have measured it out and You have plenty of room for the appropriate size furniture set out exactly as Julie Herbert last photo. But acknowledging the room size in photo is larger than yours.