[stevef]

...if secure boot is on...

Is secure boot on or off ?
It is mandatory to have secure boot off.
From the Linux Lite 8.0 release notes

Secure Boot is not supported on Series 8. You must disable Secure Boot in firmware before installing.

could u review it ?

At what point in the install does AI tell you to run the command ?

[Abhi_245]

secure boot is turned off already.

it told me to just boot the live environment and just paste the command in terminal  to get it working ; without reinstalling anything.

[stevef]

Sorry, but I don't yet understand what is wrong with your installation and don't have a fix at the moment.
Dual booting with manual partitioning seems a tricky combination, but I don't have any suitable systems on which to attempt to reproduce your scenario.

I've done a couple of dual boot systems installing Linux Lite 8 alongside another Linux version without a problem.
I've not done any dual boot systems with windows and Lite version 8, but I would expect Calamares to detect windows as a existing OS and install Lite 8 properly without needing efibootmgr intervention.
My experience is that erase disk works well on reasonably recent hardware and can be made to work on very old hardware.

During testing, I tried about 10 installs with manual partitioning and found it very easy to end with a non-booting system.

You asked me to review the AI suggested command.

could u review it ?

Code:

sudo efibootmgr -c -d /dev/sda2 -p 1 -L "Linux Lite" -l '\EFI\Linux_Lite\grubx64.efi'

-c means adding a new entry c=create
-d specifies the boot device, typically this would be /dev/sdX where X is a letter denoting the boot device on your system - not sure why '2' is suggested
-p is the number of the EFI system partition
-L is a label for the new entry on the boot manager
-l is the path to the boot loader

[Abhi_245]

Code:

sudo efibootmgr -c -d /dev/sda2 -p 1 -L "Linux Lite" -l '\EFI\Linux_Lite\grubx64.efi'

-c means adding a new entry c=create
-d specifies the boot device, typically this would be /dev/sdX where X is a letter denoting the boot device on your system - not sure why '2' is suggested
-p is the number of the EFI system partition
-L is a label for the new entry on the boot manager
-l is the path to the boot loader

Finally got it to boot. 
The code worked . 
Only correction was that after the p flag it should have been 2 instead of 1 
cuz the efi part was on dev/sda2