Single-family house, 3 children's rooms, 2 bathrooms, approximately 10.5x10.5 m²

What do you expect from the outside stairs to the basement? To me, this is only known as an invitation for burglars (work nicely with privacy screening at the door as long as you want). Leaving out the [Außentreppe], my recommendation would then be to give the garage 4m width and an attached utility room with a door to the garden.

A lean-to garage and an attached storage room behind it should only be combined if the latter is used solely for rarely moved miscellaneous items – such as winter tires and the touch-up paint, but not for bicycles or trash bins.

Wir haben auch so einen Erker, [...] sieht sehr gut aus

Here, good appearance does not apply to the bay window, but rather, growing from one side of the smoothly extended side of the house, it only makes the floor plan asymmetrical. Together with the overdosed dormer-covered gable roof, the building then becomes a complete struggle of shapes.