Do Dual-channel memory give you more Mhz speed? or GB RAM I have 8GB RAM Dual channel?

Dual channel Ram allows slightly faster access to the system Ram.

It doesn't increase the Mhz of the CPU, but allows it to work slightly faster, so it's a good thing.

no it just gives the cpu more options, its kinda like having fatter hose pipes, it can take more flow.

In each memory access cycle, dual channel allows 128 bits of data (16 bytes) to be transferred rather than 64 bits (8 bytes).

That reduces delays or wait states while the CPU is needing to transfer data to or from RAM.

It does not change the fundamental speed of the CPU.

(Imagine you are moving small items from one place to another by hand; single channel is like using one hand instead of both; working less than maximum possible rate).