How much additional cost according to the structural engineer's calculation?

Offer
as a single-family house
Plan changes from 07.01.2023
CreativHAUS Classic 143.1 including basement
 Solidly built “stone by stone” according to Building Energy Act 11/2020
 House exterior dimensions 10.63 m x 9.23 m
 Roof pitch 36°
 Knee wall 50/100 cm
 Roof overhang 50 cm
 including planning (building application) – detailed planning – structural analysis – energy certificate – awarding
 including excavation – drainage – insulation – backfilling
 including neutral construction management and construction supervision
 Excavation pit statics by client
Note: for excavation pits 4.00 m and deeper, a verification statics of the excavation pit is required – by client
 Outdoor facilities, terraces, paths, parking spaces etc. by client
 Slope protection, shoring work as well as securing adjacent buildings of any kind by client
 Demolition and disposal or removal of structural facilities of any kind by client
 Disposal of unused or non-fillable excavation material (see construction / performance description) by client
 Expenses and services resulting from requirements such as building permits, structural analysis, classifications according to earthquake zones and the like by client
 Tile material price €35.00/m² (tile formats from 30 x 30 cm to 60 x 60 cm)
 wide selection of front door models
 including controlled ventilation system from VIESSMANN VitoVent 300 with heat recovery
 including air-to-water heat pump Vitcal 200 A indoor installation instead of gas/solar
 including underfloor heating in all living rooms
 including basement with light wells according to plan

I just copied it now, it didn’t work otherwise

So everything marked as bauseits has to be done by you. That means the word bauseits. Did you think about it in advance? That’s quite a bit. Judging by your comments, you thought you were just moving in turnkey.

We do have a construction manager with whom we have been very satisfied so far

Not only in regional cases, "too big to fail" is a widespread misconception. Big Names deliberately choose corporate shells founded in the imperial era to counter the fear of bankruptcy risk ;-)

Yes, that is good. They know whose loan securities hold value, and where there is dispute over the payout of retention guarantees.

Only that "wanting to be and remain a layman" is a main motive for those who head straight to a general contractor. That hardly goes along with the need to educate oneself.