F-Droid is more than an app, it’s an entire app store featuring primarily free (as in freedom, not free beer) apps. For Android users exclusively, F-Droid isn’t just a marketplace to go side-by-side with Google Play Store, it’s full-featured enough to completely replace it. Anything you can think of: maps, games, calculators, weird niche internet configuration testing utilities: all there.
F-Droid doesn’t need Google Play to work which makes it key if you want to ditch your reliance on Google (a good idea for a variety of reasons!) F-Droid allows you to update your apps and browse for new ones. Furthermore, F-Droid is curated to keep junky or suspicious apps off the market for better user protection and provides warnings when an app has questionable practices such as in-app purchases, excessive permissions, or other consumer-unfriendly items.  
There is a downside which is that it has a much smaller inventory than Google Play store and many of the apps you’re used to may be missing (probably because they’re malicious!), but F-Droid is certainly filled out enough to be more than usable. If you’re looking to ditch the Googs or you’re looking for a list of the best open-source apps, we recommend F-droid for all your app store needs.

You can get it at https://f-droid.org