Can't install apk

[AC Question]

I have a rooted Samsung Galaxy S5 that runs on Marshmallow. If I download an apk from the web and then try to install it says always 'application in installed'. I got this with every apk that I download from the web. I also enabeld the Unknown sources.
Can someone help me? I looked everywhere but nothing helped.

 

[B. Diddy]

Welcome to Android Central! It says "Application is installed" or "Application is not installed"? What kinds of apks are you downloading, and from where? Be cautious with apks, because the sites where you find them generally won't vet them for malware.

 

[FunkyMonk3y]

Thanks for responding, it says "Application is not installed". I try to download aptoid or my boy. Before i rooted my device and split my sd card in two partitions i could install every apk from the web.