We write to explain what we have done, how we have done it, what we found, and why it matters. (Alternatively, you can rephrase all these things in a future tense when you are proposing to do research.)
Technical writing has to involve a logical structure from problem to solution to evaluation. But before you are at the stage of writing down all the details, it is often a useful exercise to write down just that logical structure. Then, your mentor can see whether the ideas hold together.