Hello,
I can only agree with my predecessors, building on the slope/incline of the property without a basement will be exciting...
I would strongly recommend a (partial) basement where the utility room can also have enough space without restricting the floor area on the ground floor accordingly.
I would also omit the gallery for the reasons Jaydee mentioned. Without the gallery, you have completely different possibilities to juggle the available space on the upper floor. For example, you could place the children's bathroom (if you really want to accommodate it on [depending on knee wall height] roughly estimated 120 - 140 sqm living space) in the currently planned gallery, then the children's rooms would also be somewhat larger than the currently drawn approx. 10 - 12 sqm. Apart from the fact that you could then manage with a single supply and drainage shaft.
Regards,
Dirk