Help with Device- apps and settings are being changed without my consent or knowledge

All I can think right now is you must have allowed or inadvertently given someone your password or sign-in key at some point. Hopefully someone with more expertise will assist you.

Disconnected the Wi-Fi and changed the password or reset your phone.

Samsung should be able to assist you remotely. Call them and see what they can do.

You signed in someone's phone or someone signed in on your phone. I have the same issue just don't know how to solve either. I know if someone downloads an app life 360 on your phone and sign in on their account and connect your phone then delete the app off your phone. They can watch your location. I've learned that recently and if you don't log out and factory rest your devices n someone starts using them they are connected to either your Samsung or Google account. Even if you look every where for evidence of them
You won't find them unless u find the device they are using it on. I gave my roommate my old phone. And everything he downloads games I get games on my phone. I tried looking in the old phone to try to delete any of me left on it can't figure it out. But has me stressed don't like someone may having access to any of my information

If it's also affecting your computer, I'd guess that someone invaded your router by exploiting open ports.  It's not hard to do if you never locked down your router by changing the administrative username and password and/or you play online multi-player games.  The default login is public knowledge and should be changed the instant your router is put into service.  

 

Take your router offline by unplugging it from the co-axial connection.  Then reset your router and log into the administrator account (if you don't know how, ask your ISP to assist you), and then change the administrator user name and password to something only you know (and for goodness' sake, write it down somewhere -Samsung Pass, perhaps). For good measure change your wi-fi network name and password.  Once that is all done, reset your phone and restore your computer to a restore point some time before this started happening. Do not restore any phone backup, set it up from scratch so that you don't reinstall any malware that may be on it. Log into your new network and then reconnect the router to the co-axial connection to bring it back online.  It's a lot of work, but this should rid you of invaders.  Always keep all your passwords to yourself.