I have changed dimmer switch in our lounge, it’s double switch, one of them is working normally, but the other one is still on and can’t switch it off or lower the light. There is more light on this switch and neither of them is working. Is it bad switch or did I connect it wrong? Thank you.![enter image description here]
You have swapped the the wires on the switch that is on all the time. There is usually 1 hot feeding the 2 switches in your case some way around you have them mixed up. A clear photo of the wires in the box and connection to the switches will give us enough info to help straighten this out. Or a detailed description of the wires and what cables they come from and where they go.