Living area incorrectly designed, ideas for changes?

Wall color light green

phew.. light green.. o_O you can really make a mistake there.. it quickly turns out somewhat "minty".

Is the discomfort caused by the color/decor or by the sound?

Our living room looks similar to your first variant. We have had several beautiful vacation pictures printed on canvas in our apartment. Such a large picture hangs behind our couch, where you have the big white wall.
That adds color and also absorbs some of the sound.

It works with sound. The uncomfortable thing adds more drive and decor for us. But I struggle as long as the couch and the TV haven't found their place. Somehow it still just doesn't look right.

Even if it unfortunately doesn't help you anymore, your floor plan and then your experience with it show what is very often suggested and advised here: swap the kitchen and living room!

Now I'm keeping my fingers crossed that you can make it even cozier. I think it's missing wood there. And I wouldn't choose gray as a wall color as well, it's already gray on gray.

I would install a wooden panel, possibly also as a room divider (often a relatively short piece is enough).
Place the TV straight on the wall.
A coffee table also in wood.
I also think it lacks wood, warm colors for the wall, as a rug, sofa cushions, etc.

As already suggested here, I would try turning the sofa, so that the backrest faces the room or the dining table, making the sofa corner visually smaller and cozier. Then put the TV on the wall where the mirror currently is. You could try that for a while and see if it feels better. If not, then a room divider, maybe also try a cheap solution before possibly having something custom-made, like a wall, for example, where the TV could also go if power can be set up there. As a color, I definitely wouldn’t choose green; I don’t think it matches the rest of the style. If it feels too cool to you and sound is also an issue: how about acoustic panels? You could clad a wall or a corner with them. Google “Woodupp,” they’re cheaper at Bauhaus.