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I had my phone undergo factory reset because there was some kind of malware and worms but it didn't work so I had it professionally fixed. And when I was going to re-install an app but it's already removed from the play store and I don't want to download from unknown sources. Is there a way to retrieve this? If there's none, what could be a good alternative for Google Play? I'm scared from unknown sources because of what happened to my phone before it was fixed.