Empty conduits on the property - ideas? - It's not too late yet :)

they have more individual parts than three fittings with threads
I still don't understand where that is supposed to be.
There are 4 sprinklers on a 2-meter diameter...

That is exactly in the middle of the lawn area Zone2(green), 1 supply line and 3x MP3000 and 1x MP2000.
Where are these sleeves? Do you mean the T-pieces with 3/4 thread on the long side?

Fittings do not fit directly behind each other (unless they are threaded).
So there must always be a piece of pipe in between.
How are you connecting the sprinkler housings? Do you have the complete connection sets? There are several options.
If you have the sets with T-pieces, do it as planned. At the end, a plug.

Not ordered yet, but the sets are not really useful in my case since the T-pieces are counterproductive, right? It would be better to use a 90-degree fitting on 1/2", on which the flexible hose is then mounted and then the MP housing. Or does that not matter for the water pressure? I also still need a plug.

So I have both. T-pieces and 90-degree elbows in 1/2". For example, if I have a line with 3 sprinklers, then 2 branch off with T-pieces and the one at the end with the 90-degree elbow.

So I have both. T-pieces and 90 degree elbows on 1/2". For example, if I have a line with 3 sprinklers, then 2 go off with T-pieces and the one at the end with the 90 degree elbow.

Shouldn't angles be avoided? Why not go straight to the last sprinkler instead of using a 90 degree?

Straight is not really possible right now. The sprinkler is, after all, positioned perpendicular to the PE pipe. The PE pipe is also only 20-50 cm under the ground. So bending it won't work either. I have the BluLock hoses for the last meter to the sprinkler. With those, you could of course make the bend a bit smoother - true. I hadn't thought of that. But it doesn't really make a huge difference now. Maybe even none at all in terms of pressure loss. I had noted somewhere. I believe about 0.01 bar pressure loss occurs with a 90-degree bend. If I don't use a 90-degree elbow fitting but make the bend gradual with BluLock, I don't have that sharp 90-degree bend but instead more (centimeter) meters of the thin 1/2" hose. That also generates pressure loss. Since the pressure loss in the end only concerns that last sprinkler, those 0.01 bar should easily be available as a buffer in the system. No one designs their system with such a tight margin.

The sprinkler doesn’t really work right now. The sprinkler is standing perpendicular to the PE pipe. The PE pipe is also only 20-50 cm under the ground. So bending it won’t work. I have the BluLock hoses for the last meter to the sprinkler. With those, you could of course make the bend a bit smoother – that’s true. I hadn’t thought of that. But it doesn’t make a huge difference now. Maybe not even any difference regarding pressure loss. I had written it down somewhere. I think about 0.01 bar pressure loss occurs at a 90-degree bend. If I don’t have a 90-degree bend fitting but instead do it with a wide bend using BluLock, I don’t have that sharp 90-degree bend but then have more (centimeter-)meters of the thin 1/2” hose. That also generates pressure loss. Since the pressure loss in the end only affects this last sprinkler, these 0.01 bar should easily be available as a buffer in the system. Nobody designs their system so tight anyway.

That’s right, probably not relevant in practice. I am currently at the beginning of my own planning, so such considerations are always quite interesting.