Alternative app store

Sometimes the play store may not have the app that you want or maybe you want a modified version of an app, in that case you can download various app stores on your phone to get the apps. Mind you not all of them are 100% safe so check before you install them.
A few of the recommended ones are:

Aptoide
AC Market
Blackmart Alpha

Note that in the last two apps, you can get various cracked games and apps for free, However you should be careful nonetheless.