Build small multi-family house - find partner in Düsseldorf area

Hello everyone,
we own an approximately 900 sqm building plot in Düsseldorf with an approved preliminary building application for a house that borders our own property/residential house.

We are considering a) selling the entire plot. b) An alternative would be to build a multi-family house on the plot (total living space approx. 180 sqm, 2-3 residential units would be possible) and to buy/keep one of the residential units as a capital investment.

An important condition for us is that in option b) we would like to sell shares of the property at short notice because we need the proceeds for a renovation. We would finance our share of the new building through a bank. Is such a structure realistic?

We would like to have discussions with suitable partners. Do you have any tips for architects or construction companies in the region? What is the best way to search?

Living area total approx. 180 sqm, 2-3 residential units would be possible

That is a scale that is too "peanuts" for classic investors.

Would like to sell shares of the property quickly because we need the proceeds for a renovation

Shares of properties are difficult to transfer, and a fund with only one property inside will not find interest. A purpose-fulfilling solution can probably be found, but not in this way.

and to buy/keep one residential unit as a capital investment

I would consider a corresponding share in a company to be more practically feasible. Basically, this is an approach that is not so uncommon, so it is not the first time a solution is sought.