Here is my product: https://matchkraft.com/. It is a marketing toolkit. I think you need to ask for feedback, asking why users don't want to pay for a premium subscription. So far, you are getting new users that is a good sign you are going to the right direction. Maybe, who is your ideal customer or maybe your product is ok but need more visibility (maybe paying ads). Try to get active users. I really want to... Source: about 1 year ago

Calling a 3rd party API: There is a complete ecosystem providing "google-sheets-as-DB". I personally tested and recommend https://sheetson.com/ but there are a lot more with free tiers https://sheetsu.com/ https://sheety.co/. Source: about 2 years ago

The resources – With Sketch, it’s impossible to run out of resources and ideas. The software’s documentation page alone has a vast number of sections that make it effortless to learn the software, plus, if you are looking for inspiration, simply visit websites like Sketch Repo or Sketch App Resource where you can find thousands of finalized designs which you can download. With Sketch, you never have to start... - Source: dev.to / almost 2 years ago