If you don't want to say "about," you can use "discuss" instead of "talk" discuss X=talk about X We discussed dogs=we talked about dogs We'll discuss it later=We'll talk about it later OR, you could erase "it" "We'll talk later" is a fine sentence

I think: Hablaremos luego = We'll talk later Lo hablaremos luego = We'll talk about it later. It's a simple thing: In Spanish, 'hablar' can have a direct object (lo) but 'talk' in English can't. eg: let's talk. talk TO me. talk ABOUT something, etc. Your second question: 'talk something over' is a different meaning, like discuss the good things (pros) and bad things (cons) and make a decision together. :)

"We'll talk it later" is incorrect.