Is there any way to install .apk files in my Lumia 640

I am using Lumia 640 device....and I am a non- insider
Is there any way to install .apk files in my Lumia 640
( i need criminal case, gom player and some apps)
And is there any way to stop whatsapp from increasing its size...(once it got 1.16gb)
often I uninstall and reinstall it ... is there any other way... pls suggest...

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