Go to AI Studio, select Gemini Pro, give it your code, or describe a problem you want to solve, and then tell it that you want to --> discuss <-- the code. That you don't want it to generate code for you, but that you want to discuss it, that you want it to comment on your code or on how to solve the problem.

This is the best way to get Gemini to be a really good assistant, unless you want to add System Instructions which precisely describe how it should behave.

Because if you just say it should solve some problem for you, it eagerly will generate a lot of code for you, or add a lot of code to the clean code which you provided.