CAUTION:
Updating manually to a new version of the Android OS may BRICK your smartphone. And before you start anything, make sure your smartphone has enough battery juice.
Usually it takes a longer time that your android smartphone will be updated to a new version of Android Operating System (e.g. Nougat Version 7.0 - 7.1.2 or Oreo Version 8.0 - 8.1) due to two main reasons:
1. The OEMs is late to release new version of the android OS.
2. The Network Carrier is also late to release the OS after a few months or years of released from the OEMs.
Here is a quick guide to update manually your Android Smartphone:
1. Download the latest firmware of your smartphone model from Samsung or Sammobile website.
https://www.sammobile.com/firmwares/
2. Download the Samsung USB Driver for Mobile Phone to your PC. To do this, you have to download the proprietary software of Samsung Kies: https://www.samsung.com/us/support/owners/app/kies, and from there update or reinstall device driver.
3. Download the latest update of the Odin software.
https://odindownload.com/download/#.WoUk5vmWZxA
4. Extract the .zip file of the new software to your computer's desktop
5. Set your smartphone in Download Mode. To do this, press the Power, Home and Volume Down simultaneously in about 10 seconds or more. Then, press Volume Up to continue.
6. Run the Odin and attach the USB cable connecting to your PC and Smartphone, and check the word says "Added" in the log.
Then attach the extracted files (BL, AP, CP and HOME_CSC) for new model of Samsung galaxies. Press Start.
(In my first attempt, I just attached AP as per tutorial of some threads at XDA developer but it didn't work. I happen to read further threads that says that BL, AP, CP and HOME_CSC file has to be attached and it works smoothly).
If the download is successful, a PASS will appear on the Odin.
7. Wait until the download finished and your phone will reboot.
ENJOY!