A few questions about programming first dmr radio

[eefpod2000]

Hi everyone!

I just got a dmr radio (radtel rt-4d) and I'm trying to program a few repeaters, but I am having some issues.
The questions I have are
The repeaters has a receive and transmit frequency, my radio says it's connected to the repeater only when they are the same, why is that?
If the repeater doesn't list any talk groups do I put in my own from for example pistar.uk?
How many talk groups can I include in a repeater?
Do I need a disconnect talk group? Do I call "disconnect" to disconnect from the repeater?

Any answers would be a big help.

Thanks,

KO4HQV