Uninstall those apps from your device, and also those that you installed just before the trouble began, unless they're obviously good ones.
Tell us what happens.
Hello and welcome to Android Central Forums..
May I know when all this started....i believe there's an app/ bloatware that is causing the unwanted downloads...kindly uninstall it or disable it..
Go to settings ...then Apps...and find out the related app that you believe is causing this..
Let us know..