Save construction costs on a turnkey house

Hey guys! Next year it will (hopefully) get serious and I will start building the house. The house is to be built turnkey and with a basement. Currently, I am waiting for offers from various construction companies. Now to my question. I have a budget of about €280,000 and the legitimate concern that it will not be enough. Where could I sensibly save costs during construction? Do the painting work myself? Only finish the children's rooms when they are needed? Build the roof/carport of the garage myself? (In case my father-in-law would help me ^^) I would really be grateful for helpful tips :) By the way, the house will be about 8.61 x 10.49 and has a dormer. Picture will be provided later ;)

Here is the photo

Use the garage. Use the basement. Then you'll get along well with your money :)

The basement can definitely not be removed. Then I would have to completely throw the entire planning overboard and would need an additional room on the ground floor. No, I don't feel good about that.

...for an additional room, you are building an expensive basement ;) ?!

Belief gone. Basement gone. Then you'll manage well with your money :)

... House gone ;)
Then the money will be enough.

Sorry, all very little input. Added a simple catalog image. For now, I consider this a troll thread, but I am happy to be proven wrong later.