"Further" is generally correct as an adverb meaning "to a greater extent or degree."
* Example: "We need to further investigate this issue."
"Further discuss" is correct if you're specifically talking about continuing a discussion.
* Example: "Let's further discuss the project timeline."
In some cases, you can use "further" alone if the meaning of "discuss" is implied.
* Example: "We'll need to further the conversation with the stakeholders." (Here, "further" implies "further discussion".)
Here's a simple rule of thumb:
* If you're talking about continuing a discussion, use "further discuss."
* If you're talking about going more in-depth in general, use "further."
Let me know if you have a specific sentence you'd like me to help you with!