What do you mean by "app menu"? Do you mean the "app drawer" (scrolling list or pages of app icons for all installed apps), or a shortcut to settings? And have you had any system updates recently?
I ask because swiping up from the bottom of the screen to access the app drawer has been an option for Android navigation for a couple of years now, so it's possible it's something you've activated accidentally or where the default has been changed by an update. I've never heard of a vertical line, but that may be a Samsung thing. So I'd check your launcher's settings (anything "gesture" or "navigation" related), and also look at the system settings for gestures (these are under "Settings > System" on more stock devices, but Samsung change the Settings layout so I can't be fore where they'll be on your phone).