2 taps, but only one inlet and outlet

Yes, the cables have been laid so far.

I still haven't understood whether the walls are already closed or still "open".

Therefore -> picture

Moment, is it about the inflow or the outflow now? First you talk about two taps and then about a 50mm pipe, that doesn't match. Yes, a picture would be helpful...

There is a suitable solution for everything. For your one cold supply line, simply use an angle valve with two outlets, see kitchen for cold and dishwasher. Of course, there is also one for hot water, where you do it basically the same way. And for your wastewater, there are T or Y pieces into which an Siphon each goes....

The same happened with us during the sampling, we didn't think about it and then the wife wanted a double washbasin.

I installed a double angle valve on the cold water and on the hot water, which was available at Bauhaus.

And a double HT distributor on the drain.

So far so good.

Since we have two drawers next to each other, the divider was exactly at the drain...

So I sawed a bit on the cabinet until it fit. But it has been like that for 5 years.

I will send a picture later.
The wall is completely closed; but without tiles, as we are not using tiles around the washbasin.
I now fear the next outcry.
We will paint the area twice with latex paint (after a normal preliminary coat).

To explain again: We have installed an inlet and outlet in the closed wall.
From the inlet, I now need to get two lines to two faucets. So far, I haven’t seen any problems here. In the kitchen, we have already solved it this way because we have a side-by-side refrigerator with a fixed water connection.

I am still looking for a solution for the outlet.
I was looking exactly for something like what described.

I didn’t find anything like that at our hardware store.
So I guess I have to go to the big stores.

Since we have 2 drawers next to each other, the dividing wall was exactly at the outlet...

So we sawed a bit on the cabinet until it fit. But it has been holding up for 5 years.

I already see that coming for us too.

Background on the timing:
The bathroom upstairs is not quite finished yet (new build) and the washbasin has not yet been held in front of the wall, etc.
I just wanted to take care of the upcoming plumbing early since I want to be able to use the bathroom immediately once the washbasin is installed.

The bathroom has been a construction site since we moved in (01.06.20) because the plumber forgot to install a part in the concealed shower. Therefore, the first demolition work already took place in the new build yesterday.

Ah, just google "Ablaufgarnitur Doppelwaschtisch" - you'll get myriads of options...