Vertical scrolling in the app drawer is a huge UI revision in Android Marshmallow, one that can prove quite jarring at first. While you might opt for a third-party launcher to overcome this problem, another option exists.
Although a temporary fix, you can revert to the old left or right scrolling user interface in the app drawer by uninstalling a Google app update. Do this by opening Google Play, tapping the three-dots menu and selecting My Apps. From here scroll down to Recently Updated and find Google, then tap Uninstall.
Agree to uninstall the app and then wait. If Android hangs for any length of time, hit the Home button or restart. When everything is back to normal, you will see a Welcome flash as if you’ve just installed Android or reset to factory settings. Tap the Home button to see the old-style app drawer!