3 LIGHTS TO 3-GANG SWITCH

All 3 switches should be grounded, plus one box should have a ground wire to the box ground screw, all ground wires into the 3 gang should be connected together, run a 4th to the metal box and one to each switch ground.

You have 2-gang switch.
Look at following illustration showing gang switches:
http://waterheatertimer.org/How-to-wire-switches.html#gang

Hot wire feeds one screw on first switch, and then jumpers to second switch.
Your jumper wire is connected wrong place.

Find hot wire... there will be 1 hot wire entering gang box.
Disconnect all wires, and separate for testing.
Turn power on and test each wire to bare ground wire... that will show the hot wire.

Sorry it is difficult to post question on fixya, or communicate with people answering free questions.

Gene h

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I can probably help.
BUT, what voltage are you working with. It sounds like 230V european wire colors?
Now also. Do you have two separate light switches in same box (which is called 2-gang)? Or do you have a double switch, which is two switches on one device?
Add a comment, and include as much detail as possible about the switch, voltage, and number and color of screws on each switch.
Here is a start-point using 120Volt and US wire colors:
http://waterheatertimer.org/How-to-wire-switches.html#double
The difference between US and European, is that European has two hot wires, while US has hot and neutral wires. Otherwise both systems require two wires to complete circuit.

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Okaaay, but which is the permanent live from the lighting circuit, which is the switched live back to the ceiling light, which is the neutral from the lighting circuit?
You may need to open the ceiling rose to see how the red/yellow/blue are wired.
On the switch the terminals are usually diagonal, ie L on the top matches with L1 and L2 on the bottom. L1 and L2 on the top match with L on the bottom.
So you want permanent live from the lighting circuit to go to L and a short piece of wire linking that to the other L.
One of the L1 is switched live back to the lighting circuit.
Other L1 is switched live to the cabinet light. (Red?)
Presumably you also need to connect the neutral from the lighting circuit to the neutral to the cabinet light. (Black?)
bedroom lights

I'm sorry, maybe I'm not understanding correctly and completely. First, I'm assuming you're installing a two gang box to replace an existing single. If not and you have two red and one black terminated to your existing switch, all you should have to to is; kill the breaker, remove the existing switch, get a couple spare pieces of black wire, just to keep things consistent, splice the three black wires together, terminating one on each switch, top or bottom doesn't matter, and carry one red to each switch. That's about as simple as I can explain it. From everything you've said, your black sounds like your hot wire, and your reds go to either light fixture. This installation should work for you hope this helps!

Copy following link for wiring 3-gang switch:
http://waterheatertimer.org/How-to-wire-switches.html#gang

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What is 1mm double core?
Following image shows example 120Volt 4 gang switches with outlet.
http://waterheatertimer.org/images/Single-pole-switches-in-4-g.jpg
Each 120Volt electrical box has one Hot wire. This is true for ceiling and wall boxes.
Normally in a gang box, the Hot wire jumpers across all devices in the box.
Some switch boxes do not have Neutral wire. Neutral wires are usually white, and are twisted together and covered with wire nut and shoved to back of box.
Open following links for typical 120V and 240V circuits in US.
http://waterheatertimer.org/B220C.html
http://waterheatertimer.org/See-inside-main-breaker-box.html

Feel free to add a comment and describe wiring, and voltage.
For example if hot wire arrives from one of the lights.
Describe the wires that you have, and what each wire goes to for best possible answer.

Open following links for images of 3-gang and 4-gang single-pole switches.
With the 4 gang, just subtract one of the switches.
http://waterheatertimer.org/images/Single-pole-switches-in-4-g.jpg
http://waterheatertimer.org/images/despard-500.jpg

If you have a 3-way switch, or outlet in the box, then add a comment with more exact information about what wires you are trying to connect, what color wires you have, and what you have tried so far. This will narrow down the possible answers and speed help.

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First you need to make sure that you do have a hot feed in this box. Do you have a circuit tester?

before u start make sure power is off before working with electrical lines ---start with the 12/2 coming into box black [power] white [ground-neutral] and u will have 3 separate lines for the lights so u will have 4 lines total coming in the box== with the 3 light lines take the white and strip back the plastic and connect [wire nut] all 3 to the 12/2 white line --now take the 12/2 black line and connect it to the first switch gold color screw- bottom screw -now take some wire about 2-3 inch strip both ends and connect from the 12/2 black wire connection on the switch and connect to the gold /bottom of switch 2 than do the same for switch 3 connecting the wire from switch 2 so u will have power feeding all 3 switches-- now connect the black lines for the lights to the other side of each switch and ur done