It is not fundamentally wrong, but it is certainly not a must. The hand should also be held in front of the mouth when yawning. Not everyone does that either.
If I read your site plan correctly, only the street in the area of the curve is above your ground level/top edge of the finished floor. The rainwater will flow into the gullies there due to the existing curb. I don't see a problem that your place could be flooded at first.
I don't see the problem. That it might still be nice to be a few centimeters above street level is almost a matter of taste.
My ground level is given as 70.50. Thus, the majority of the street is above the ground level, partly by -17 cm (to the street edge height).
The top edge of the finished floor is planned at 70.65 and you are right, thus it lies only lower than the street height in the curve,
but...
... the street edge height should not be neglected either, right? Street edge height = street height + 8 cm.