Sales: Read founding sales by Kazanjy
Management: Read 'the effective manager' book and 'if you want something done right you don't need to do it yourself'
Hiring: Do as little as possible; if something doesn't feel right and it'd be painful to unwind then don't do it. Consider "cell division" hiring (https://medium.com/newco/who-should-a-startup-hire-first-c12...)
Marketing: talk to your existing customers that came inbound, figure out where they found you, double down on that. basically look for what channels are already working without any effort, and then put effort into them
Mostly it's just - sell more and do the marketing, and then all the hiring and management challenges will be painful but they're more deterministic and will be solved. What I'm trying to say in this last paragraph is that direct all of your effort to the sales and marketing, and the hiring and management stuff will come up when it comes up and is painful, you'll solve it, you'll move on. But without direct effort on the sales and marketing, it won't happen. I.e. the hiring and management is pain driven and will force you to solve it, the sales and marketing won't force you to do it, so put your effort there, because your effort will naturally be pulled to the hiring and management as needed.
And in general, trust your gut. Do what feels right even if it's "weird". You are the expert on what you want, on your business, and so on - so seek info like you're doing but if something tells you that a given approach doesn't feel right, then trust that intuition and find another approach.