2 way dimmer that drives me mad?

I have a 2 way, 2-gang dimmer switch that supposed to switch the lights in two separate rooms. One of the lights it is also connected to another regular switch. The dimmer has in the box 2 main wires with 2 reds and an earth each and the third one has a blue a yellow, a red and earth. I know that the first two I mentioned are from the lights in the two rooms and the one with the more colourful wire it’s the other switch. I tried all sorts of comb but I only manage to get the lights in one room to work or both in the same time on the same gang. There is no l1 and l2 in the back of the switch but only an L, an Sw and a symbol like a wave thing with an arrow. (it is the same in the back of both gangs)
Pls some help with this. It drives me absolutely mad!