Is my budget sufficient? 210 thousand euros for a single-family house

May I ask why only below? Why not leave it out entirely?
Burglary protection can't be the reason.
.

Less for burglary protection, although with aluminum shutters at least there is a "noise and attention factor." At least that deterred the last burglars at our place.
But more importantly, everyone can look in from below in the evening. It’s already more difficult from above.

We might retrofit exterior blinds above later. At first I thought the idea was silly but then I saw really great ones at a fair...

In contrast to the roller shutters, ..., cistern, geothermal energy, ..., etc. are luxury to me.

The cistern is often not a luxury but a MUST. With us, it is required that the builder installs an infiltration system. Therefore, a soakaway, soak pit, pond must necessarily be constructed. According to information from our construction company, placing a cistern before the soakaway (which can then be smaller) is hardly more expensive than the (large) soakaway itself.

What I want to say is: There are regulations according to which, for example, a cistern is not a luxury but a necessity.

And regarding geothermal energy – well: Whether I install a cheaper heating system today and have higher annual operating costs in the long run, or install a more expensive heating system (geothermal) that pays off in the long term, everyone has to decide for themselves. Thus, this would (considered in the long term) not be a luxury for me either. Writes someone who will build with geothermal energy :o.

It might currently be trendy to plan for roller shutters.
By the way, good sun protection is very important nowadays in highly insulated houses – a few years ago, roller shutters were installed as cold protection in front of windows. Also, burglary protection.
Nevertheless, I find it exaggerated to equip all windows with those - not exactly attractive - things.
But that is a personal opinion.

Still, one should not demotivate someone who can only afford a slightly more frugal house with such personal opinions.

These opinions also include statements (not mentioned here now, but often read/heard) like "Bathroom under 10 sqm is social housing," "a house belongs to a garage," "you only build once," and so on...
Everyone has their own personal standard – how it came about can only be said by the one who set it. And it can also be adjusted or changed if necessary. We are talking about standards.

Our house with approx. 135 sqm (reputable construction company from Lower Saxony) would have cost around 145,000 turnkey "naked" according to the 2009 Energy Saving Ordinance (ready to wallpaper and floor coverings in EL). ("Naked" means, for us, that further upgrades were important.) Add a (now obligatory) controlled residential ventilation system and a few special services, we come to 160,000. No tile upgrades (there are also nice tiles for 25 €), laminate in the living area, converted kitchen, normal shower, rough work in EL, etc., we come to 180,000. Plus ancillary construction costs.
Garage and external pipe for chimney can be retrofitted. Paths and yard can be filled with gravel.

We just don’t know how the TE’s maximum budget is composed, whether buffers are available, or special payments have already been planned.
Where or for whom/how many people the house is to be built.

Addition: my owner-occupied comfort apartment from a few years ago (it still exists, by the way) has no garage, no roller shutter, no walk-in shower, and no underfloor heating. Nevertheless, it has been lived in well and comfortably.

However, one should not demotivate someone who can only afford a somewhat more economical house with such personal opinions.

Thank you very much for the support, in case that was also directed at me, among others. I must admit, however, that our "normal house," although without the extras, is somewhat larger. That was more important to us than roller shutters. To each their own pleasure, after all. :)

Many thanks for the encouragement, if that was partly directed at me. I must admit, however, that our "normal house" is somewhat bigger, though without the extras. That was more important to us than roller shutters. To each their own pleasure. :)

Nooo, it was referring to "Therefore still, if you are really honest and build solidly (roller shutters belong on all windows) then 300 bucks are gone." :)

Regarding the point shutters in summer:
Shutter down: Sun protection guaranteed, but the room is pitch dark and not usable (except for sleeping)
External venetian blinds down: Sun protection guaranteed, but due to the possible tilt of the slats, enough indirect light still enters the room. Room remains usable.

External venetian blinds cost about 20% to 30% more, but in my opinion are a worthwhile alternative for living spaces ([Ess], [Wohn], [Kinder], [Küche])