Hi Jack,
Product marketing is mainly about users journeys and pain points and creating out the messaging out of it.
1. Gtm mostly go to market strategies, what all you need before launching,create a to do list for it.
2. Positioning why you are different than your competitors and what you can offer which your competitor can't offer.
3. Messaging How do you convey your message in the user segment which makes people click and relate.
Mostly these are the things, you can work out with your sales guy to understand where you are losing the deals or you can interview your users to understand what kind of problem they are trying to solve but can't.
I hope that helps. If you are hiring for a product marketing manager, please let me know.
Or you can DM me if you have any more questions.