Floor plan design single-family house with around 150 m²

2.5 m is already quite tight even with chairs pushed in. A 90 cm table with the chairs is then about 120 cm, leaving a maximum of 65 cm on both sides for main walkways. And that is already not very generous.

Here, there is no other option but to choose a table that is as flexible as possible ... e.g. about 90x140, which can be extended in ideally 2 stages up to about 240/260 cm. This should provide a reasonably decent solution for everyday use (there are then setup options that can be tried out), but also be flexible with guests.

As a recommendation for interested readers and future homeowners: always include realistic furnishings in floor plans and also measure the distances that result, if necessary simulate the situation to get an impression of how the distances feel. Also always think through "life situations," when do you want to use the terrace door? What do you do then, when do you need a larger distance, when is the minimum enough, etc.?

2.5 m is already quite tight even with chairs pushed in. A 90 cm table with the chairs then has about 120 cm, leaving only a maximum of 65 cm on both sides for main walkways. And that is already not very generous.

He has a width of 4.32 m there. The OP calculates the 2.5 m as the space requirement of the table + chairs, which comes to 1.20 m. Our dining table measures 2.50 m x 1.2 m; I quickly held the measuring tape to it last night and with loosely placed chairs (i.e., not properly pushed in), the space requirement was about 2 m.

At the bottom of the plan is a fireplace, which according to has become very large. Also, you should keep some distance from it, at least if you are using it, otherwise your backside will get pretty hot .

Tendentially, I would rather place the table as shown in the drawing and make sure I have about 80 to 100 cm of clearance upwards in normal size ... after all, it is a sliding door and ideally also about 80 to 100 cm to the piano.

I think anyway that the path to the terrace is much more often taken from the hallway or the kitchen than from the sofa.

Even at the risk of repeating myself: in case of a visit, you can also turn the table out of its everyday position, and the man at the piano can wait for his beer - anyway, there is none in Hawaii.
A piano, a piano - Mother, we thank you!
And the fireplace can stay off when people are sitting cozy and close around the table - even in a pre-energy-saving regulation house it would be like that.

I would laugh if the Greens were to ban fireplaces soon.

At the bottom of the plan there is still a fireplace, which according to has become very large. You should also keep your distance from it, at least if you use it, otherwise your backside will get pretty hot .

Tendentially, I would place the table more like in the drawing and make sure that there is about 80 to 100 cm of space upwards in normal size ... it's a sliding door, and also preferably 80 to 100 cm to the piano.

I think anyway that the route to the terrace is taken much more often from the hallway or the kitchen than from the sofa.

Yes, unfortunately the fireplace is not visible, I will draw it in tomorrow. It sticks out about 90x50 next to/in front of the chimney, so the table really cannot be pushed that close, otherwise it will be too hot and the passage too narrow. I also think there should be at least about 80 cm of space upwards. As for the piano, it depends on how far the chair is pushed in.