Split the underground cable into 2 circuits

Would it now be possible to connect 1x constant power (sockets and lighting in the garden house) and 2x separately switchable (1x lighting in the garden, 1x well in the garden)?

Yes

oh wow, 100m is quite a distance
For that, if you want 16A, you need a 10mm² underground cable

Yes

Thank you very much! That opens up completely new possibilities! So far, I have always assumed only 1x continuous power, 1x switchable.

Thank you very much! This opens up completely new possibilities! So far, I have always assumed 1x constant power, 1x switchable.

But watch the total current if the blue serves as the only neutral conductor and not very long distances as mentioned above.

Oops ok.

Well, the 100m was generously rounded up. But just the cable from the terrace to the consumer could already reach 50m. If you also count the cable inside the house, 100m is not that exaggerated.

I think in the end one loop will be 10m and the other 50m. (Measured from the terrace)

But the underground cable that's currently there is only 2.5mm² if I remember correctly. Then a thicker cable in the rest of the garden wouldn't really help me, would it?

No, it doesn't really help, because the "bottleneck" would be the transition to the cable with 2.5 sqmm. So, as someone here already wrote, a transition box or field distribution box would be good. There you put a 6A fuse for the 50m cable and a 16A for the 10m cable. But only if you use 2x neutral conductors.