We struggle with the position of the sofas in both options. It seams like there is not enough space for them, even there is such a big room...

Two options we see. Maybe they are more... but we just don't see them...

Maybe one more thing, we have often visitors, big groups of people and we actually hoped there would be space for at least 8 person to be seated on the sofas. So both solutions above don't really match our needs.

Maybe you could consider a see-thru fireplace to separate your living and dining areas. You don't have to build a whole wall, just enough for framing. You could then use the extra space for chairs.

You would have to move the couch a bit to the left for a see-thru.

We thought about it, but we have the master bedroom above the dining area, so the chimney would go right through the room. Or where would you place the chimney?

How would that idea help at all. The space is too small with dining and LR IMO this floor plan has too much wasted space all that space behind the sofas in just wasted so yes you have lots of footage but not well thought out.

Do you have an advice/proposal what we could/should we do differently?

Our floor plan looks like this, because we have in the level below an additional apartment, witch can be used as an office. So we tried combine all that in the allowed footage. So in some areas there is waste of space, in other it is a little bit tight. But it was the best we could do... now we try to deal with all the compromises.

You don't need a chimney with a gas fireplace, you just need space for venting. You could vent out the wall between that level and the bedrooms upstairs.