Solar storage for photovoltaic system?

You can first search for the Photovoltaic Calculator from Finanztest and play around with your details there.

It might also make sense to use a hybrid inverter and only upgrade it later when storage becomes cheaper.

But also tell me what kind of roof ([Pult, Sattel, Flach, Ausrichtung, Bedeckungsart...]) you exactly have. What structures and what dimensions? Is there perhaps a garden shed or a garage directly next to it?

I would first invest the (financial) strength into a proper plan and clarify whether really no more than 5kWp fits on the roof. That is better than nothing, but for our prospective needs with heat pump and electric car, it is rather small. What is the roof pitch? Which directions do the roofs face? Is there a garage, carport, garden shed?

It is a terraced house, keep that in mind, right?