I had the same question about drainage, etc.:
Back then they said several meters to the downpipe was no problem?
And slope according to DIN: 0.5 cm per meter = 0.5 percent. (Okay, that was from me. But nobody objected either )
I would lead the wastewater towards the HAR and then via downpipe under the slab and then away from the house!? A downpipe in the HAR, possibly covered, doesn't really bother, does it!?
Coffee grinders are square or approximately square.
The staircase is specified with a rise of 19.2.
3.52m as raw construction width of the bedroom is possibly or possibly not a bit tight. About 3.49m remain after plaster, if everything fits and with a bed 2.10m wide (including frame) 69.5cm per side.
The space for a passage right side of the dining table and then behind that space for a cabinet (how much space is needed in front of it to the chairs? At least 1 meter to open the cabinet and still stand far enough away from it to open it).
At the moment I really see no storage areas at all. There is no basement. OK. There is a carport, no garage. OK. But the HAR is of course very small and the utility room upstairs =>!?
Where will the laundry be collected, where will the laundry be sorted, where will the laundry be hung up (or is EVERYTHING supposed to go in the dryer all year round? Especially with the controlled ventilation you can hang laundry indoors all year round. And as far as I know not everything can go into the dryer if you want it to last...).
Bicycles, garden furniture, grill, sunshades, supplies, beer crates, water crates, wine bottles, other drinks, Bobby car, seasonal items (Easter, Christmas, carnival, Halloween just like summer and winter clothes, sled, bathing toys for summer, ...). Drying racks for things that don’t or can’t go in the dryer. Dollhouse, garden tools, ironing space, space to sort laundry, toolbox, drill, children’s old school stuff. The fuse box is not drawn in either. Also many pipes run in the HAR. Water connection (pressure reducer, fine filter, meter), gas, electricity and telecom need space. Media server? Patch panel? Sporadically used kitchen appliances. Inline skates. Ski equipment.
Not that all of this necessarily applies, but you know how garages look these days in new development areas or that eventually the second garden shed is added...
Especially regarding the garden, a lot more comes along if you haven’t had a garden before. Surely also lots of children’s garden toys that shouldn’t be left outside during storms, hail, frost or snow.
I don’t mean now: don’t build a basement. But make a storage plan for the things you have and might have in the future.