Interference problem on my wireless magic sing, i can hear the voice of my neighbor using her own wireless magic sing on my sound system and vice-versa, it's annoying. what should i do?

Hi
If you know anything about RF stages of your unit you may be able to adjust IF transformer next to the crystal and do the same little adjustment in the receiving stages of the receiver.

I have Magic Sing ET19V model. My wireless mic will turn on then off but if i move almost touching the base unit the wireless mic will be o. Any solution?

The magic sing has an omnidirectional antenna which is unnecessary since you will be standing directly in front of it while using it. I recommend you take an aluminum pie plate or other aluminum piece that is larger than the antenna and place it directly behind it, perhaps even held on by tape to the antenna. You can even bend it around the antenna in the form of a V with the opening towards you, where you'll be holding the mic. This will block the other signals from your neighbor while still allow you to use it. It may even block your signals from leaking onto your neighbor's unit.