Property donation! How to proceed in a tax-optimized way?

Also an interesting point of view. But the recipient receives 3 properties from 3 owners. In any case, a professional needs to take a look at it.

Not an interesting point of view, but it is like that. The recipient pays the gift tax, not the donor. So the exemption amount also applies to the recipient. This means that the gift initially triggers an assessment for gift tax for the recipient; then it is checked how much it is; then it is checked how much exemption amount has already been used within the relevant period; if that was zero, then the whole exemption can be deducted; the rest is taxable. The exemption amount applies per recipient once every ten years, to my knowledge. Whether the sum of the current gifts before deduction of the exemption comes from one or several gifts is not relevant – and neither is the number of donors. What you inherited from Aunt Trude last year counts and reduces the exemption amount for the current gift from Uncle Otto.

Then nothing of the house will belong to you if you don’t own anything of the land.

That, in turn, is an interesting question for the tax advisor: whether one can lease the land for one’s house from one’s wife under community of property / accrued gains community / joint assessment.
Otherwise, the recommendation is: "Piano thread"

On Haufe, one can find an example where grandma and grandpa gift a property to the grandson. Here, the exemption amount is applied 2x. So, once per donor.

The gift tax allowance applies per donor. Thus, three times the allowance.

Well, that should work out. I would leave the daughter out of the equation, she will inherit anyway and it becomes even more complicated in case of separation. Divide it among yourselves, as I said, proportionally according to what each ultimately contributes to the house construction including the land, and make each other sole heirs according to the [Berliner Testament]. The daughter inherits it without any problems, if there are no other higher assets, a normal single-family house is below the exemption amount for children. But if one partner dies and you don't appoint each other as sole heirs, then the child inherits as well and suddenly you can no longer decide alone about your house.

Since there are different tax exemptions for the recipient / heir depending on various degrees of kinship, your model cannot be correct. It is as shown here by, among others, .