Any ideas for the struggles of a N3?

You mention that you’re reading manga but you don’t mention books. I can definitely recommend reading books, even if you’re more interested in listening in the long run. But it gives you good exposure to grammar and vocab at a pace that you can determine yourself. For many books N3 is pretty sufficient, so that would be a very good match for you. If you like to read in a group, you could check out the Intermediate Book Club here in the forums; we will start our next pick next month, so it’s good timing for you! Or else, you can read the past picks and make use of the discussion threads.