Help with light switch conversion to dimmer switch?

I have a 2 gang, 2 switch wall switch and want to replace it with a 2 gang, 2 switch dimmer switch. The dimmer switch has two sets of 3 wire in attachements, but the old light switch has lots of red wires etc., L1, L2, L3, fitted and I dont know what goes where. A wiring diagram of old fixing and then new fixing with wire colours etc., would be great, as I have searched and searched but cannot find anything that will remotely help me on the internet. Please can a kind electrician help me?
Thank you. Please email me replies to:
Rainbird150@hotmail.com

I can email pic of wiring at back of old plug if it would help.

Thank you
Julie