So regardless of the layout, if I move the garden to the south I initially have sun. But if someone builds a house on plot 152/2, I’m right back where we started.
Why? The sun’s path doesn’t change because of that. Even a development south of your property would at least overshadow the high midday sun on most days of the year.
I see a lot of trees on parcel 152/2 in the aerial photo. Is part of that possibly also on your property? You could then keep them as a privacy screen in case of an unattractive neighboring building. I also don’t think the neighbor is allowed to radically clear-cut all the trees when building; does the municipality have a tree protection ordinance? The shadow cast by these trees isn’t very long in this picture either; you would still have plenty of sun in the garden if you plan your house in the north and the garden in the south.
Are these deciduous or coniferous trees (asking because of light transmission in winter)?
Therefore, I would tend to place the house directly 3m from the southern boundary, garage to the north, and the garden in the northern corner of the property.
What do you think about that?
Not much, then your own house would shade the terrace and large parts of your garden during the day; towards the evening the shadow would come from the garage and in the morning probably from the trees along the eastern boundary. I would place the house as far as possible into the northern corner.
At the southern end of the garden, I would then set up a small seating area in the shade of the trees for the hot days.