Is 5000 downloads of an app within the first month a good sign

Downloads isn't a great metric to go by for success. The real value that is being offered is from your engagement rates. Whatever makes sense for your situation, Monthly active users, daily active, etc.. When an investor is investing they want to see value and a great exponential growth pattern. This is why they tend to (from what I've heard) look for those core metrics over vanity things like downloads.

Why aren't downloads a good metric?

You could easily have a bunch of people download your app (there are whole farms that do this and there are click farms to fake the core emetrics). Don't fake these, the thing you are after is a business, not an investment. In order to grow a business you need to make your users happy as they can be and telling friends to come on the app and use it for whatever purpose it is supposed to.

Maybe your app is screwing up left and right and people are downloading it multiple times or trying different accounts. Maybe the 5,000 downloads are just people downloading and uninstalling it.

See why an investor wouldn't care about downloads? User engagement, start finding your metrics on that and you'll get the answers you want (investors calling).

We were in Startup School by Y-Combinator and it talked a lot about these things.

https://www.youtube.com/watch?v=ZoqgAy3h4OM&list=PLQ-uHSnFig5MiLRb-l6yiCBGyqfVyVf17&index=1

Depends on how much you spend. If it's all organic/free traffic, that's really good! I'm interested in hearing more :)