What are the signs of product/market fit?
Well, when you want to know if you have product market fit or not, you need to pay attention on the number of downloads of the app, your users are the ones who count the most, you need to have a constantly growing number of users. When they are satisfied with the product's values, they are willing to pay for it, the word of mouth is working well and thus affects the revenue.
To understand the user behavior in your app, see what features users prefer also to know the crashes and problems occurring in the app you may need a good analytics tool.
I would recommend you to check out Inapptics | Mobile App Analytics Powered by AI, it offers various features starting from users' navigation within the app, or creating visual funnels to see how many users reach exact goal and more.
Feel free to sign up for free and good luck!!