Different share/equity for construction. How to write it firmly?

What would happen in the event of a separation? Would the house then be divided 50:50, even though I contributed significantly more equity?

I cannot provide legal advice, but to my knowledge, unless you agreed otherwise when getting married, the community of accrued gains applies. This means that at the time of marriage, it is determined who brings what into the marriage. You bring in the property and equity, your girlfriend brings nothing. The increase in value that occurs over the years with the house is shared, but not the portion that each of you brought into the marriage. In the event of a separation, some math is required... May a lawyer correct me.

otherwise, you can surely also inquire about such things at the notary, or have them registered.

Hello,

sometimes I really wonder how potential builders conclude that they are being disadvantaged when they save a few euros instead of investing them in proper advice. With a total volume with you > TEUR 400

Now it is so that I bring about €150,000 equity and my girlfriend €50,000 equity.

A forum cannot replace the notary for you, let alone that legal advice is a dangerous field for a forum operator. User Nordanney gave you the correct answer; in the event of separation, the values before the marriage remain the leverage for the approach.

We will finance the remaining €200,000 and both of us will be listed as debtors and both will repay these debts.
We will both be registered in the land register.

Then, at the time of separation, the value of the house will be determined and both assets from before the marriage will be deducted. The remainder will be divided or you will have to pay each other out mutually.

You can even maintain separation of property during the marriage and still finance the house construction together. Consult a notary you trust and clarify the worst case; that is money well invested and prevents disputes where they inevitably arise without preparation.

Rhine greetings

Hello,

just one more thing in addition: You write, you are getting the property (I assume as a gift).

Also ask before the property transfer with a notary and a tax advisor how best to proceed.

Within the family there are completely different tax exemptions than between family and (potential) daughter-in-law...

Just in case suddenly

...gift tax is at issue, which could have been avoided.