I am not real familiar with European wiring but I think this is the only way the old switch could work.
This is plain-old single phase power.
The brown wires are hot, one in from the power source and one on to the next switch or outlet. The blue wire is connecting the brown wires together (the paired holes are internally connected). The black and white wires are switched hots going to the lights (or switched outlets).
The thing that was confusing is that switch 2 is connected backwards: hot is going to the switched output side of the switch and switched hot is going to the line side. The switch really doesn't care which way the power goes, as long as you aren't using it was a (US called) 3-way switch.
For the new switch, connect the two brown wires to the "L" terminals and connect each of the black and white wires to one of the arrow terminals.