how can i update my Samsung operating system

[Android Central Question]

the operating system on my device has been modified in an unauthorized way

 

[Rukbat]

Flash the stock ROM. (Make sure you back everything up, because a stock ROM doesn't have any of your files on it - music, pictures, contacts, etc.)

See [Samsung] How to flash Stock ROM via ODIN for flashing and Backing up an Android Device for backing up.