Terrace Amendment Building Application

Hello friends,
we will build and submitted the building application this week.
We wanted to make the terrace 3 meters wide and 10 meters long ([Haus breite]). That's how we submitted it.
The terrace will be about 1.5 meters high because of the slope. Now the question is, can we extend the width of the terrace to 4 meters or is that no longer possible? What is the better way to proceed?

Do you thereby exceed the floor area ratio or other regulations? Are you building too close to the neighbors?

The floor area ratio is 0.4. How can this be calculated? The plot area is 399 sqm. Everything is fine with the neighbors.

Floor area ratio: 399 x 0.4 = 159.60 buildable area.

Apart from that, it depends on whether you have actually submitted a building application - then an employee of the building authority also comes out and inspects - or have applied through the simplified approval procedure - then your architect is liable with his signature.

What both variants have in common, however, is that if the larger terrace fits within the floor area ratio - an additional application becomes necessary.

Rhenish greetings