@SanjayGehija Hi! Try wiping your cache partition follow these steps below.
1. Turn off the device.
2. Press and hold the Volume Up key, then press and hold the Side key.
3. When the green Android logo displays, release all keys ('Installing system update' will show for about 30 - 60 seconds before showing the Android system recovery menu options).
4. Press the Volume down key several times to highlight wipe cache partition.
5. Press Side key to select.
6. Press the Volume down key to highlight yes, them and press the Side key to select.
7. When the wipe cache partition is complete, Reboot system now is highlighted.
8. Press the Side key to restart the device.
If these didn't work try updating your phone with your computer using Smart Switch
Start with download Smart Switch for your computer by going to this link - https://www.samsung.com/us/support/owners/app/smart-switch
Install the Smart Switch on your computer. Once done restart your pc to make sure that files needed are installed correctly. Then connect your phone using the cable that came with your phone to your computer.
Then an option " Update " should appear and that should update your phone if not then you must set up an appointment to have your phone get software re-flash by going to this link to look for available service center near your https://www.samsung.com/us/support/service/locations/
If these steps do not help, you will need to follow up with your service provider.
You didn't specify which device you have.
Do have enough free memory in your phone?
Try going to:
-> Next to personal applications and click on the symbol in the form of a list
-> Tick "show system apps" then press OK
-> Scroll through apps until you find "Software Updates"
-> Click on it then go to "Storage Memory"
-> At the bottom right click on "Empty Cache"
-> Restart your phone and try again to check for updates.
If you have a recent device, most likely you are having problems with your Wi-Fi connection.
You need to have a Wi-Fi connection in order not to have download problems