Paying out partner and second time real estate transfer tax

That is clear; in my opinion, it is a matter of weighing what is higher. Real estate transfer tax or gift tax; after all, it is not the purchase price at the time, but a share "x" that counts.

Or where is my flaw in thinking?

Rhenish greetings

I would replace the "or" with an "and".

Thank you for your feedback. I have not dealt with gifting so far; I suspect the tax burden is very high because we are not married. What’s more is that I don’t know if I will keep the house for 10 years, meaning if the purchase price is deliberately kept very low, the higher sales proceeds could then cost more taxes than the saved real estate transfer tax. Property prices have risen sharply in recent years (there are no properties on the market at our purchase price); under certain circumstances, it might even make sense to deliberately set the purchase price high. I think I will just handle it by using the original purchase price; thanks again anyway.

If you live in the house yourself, the 10-year speculation period does not apply. You only have to have lived in the house in the year of sale and in the 2 years prior, then the sale is tax-free. Partial years also count. For example, if you moved in December 2014, you could sell the house tax-free from January 2016.

in my opinion, it is a matter of weighing which is higher: property transfer tax or gift tax; after all, it is not the original acquisition price that counts, but a share "x".

I agree with that. If she sells her share to him, property transfer tax is due. If she gifts her share to him, gift tax is due. AFAIK, it can be contractually regulated who pays what in this case.

Living there for the two years prior is by the way not necessary!

I agree. If she sells her share to him, real estate transfer tax is due. If she gifts her share to him, gift tax is due. AFAIK, it can be contractually agreed who pays what.

The tax debtor for the real estate transfer tax is generally the buyer (=purchaser).
Of course, the seller can grant the buyer a sum x as a concession. But since this is a side agreement, it must be included in the notarized purchase contract.
If x happens to correspond to the real estate transfer tax...

Real estate transfer tax can be avoided in the case of a gift. However, if the gift is not a genuine gift (I assume your ex-partner won't simply want to gift you half the house) but a gift under the condition that you take over the loan, then gift tax is due. That will definitely cost you more.

For expensive properties, a company is usually founded, which pays the real estate transfer tax once upon acquisition.
Afterwards, the property itself is no longer transferred, but 95% of the company that owns the property.
This is how the big players in Germany save millions (as recently again at Potsdamer Platz..), but the small farmer or homeowner is burdened.