How to share partitions?

You always share a folder, the fact that it is a separate partition is irrelevant in Linux. It is seen as a folder just like all the other file systems your OS uses. It's accessed in the same way rather than Windows with clunky drive letters.

Does this help
https://www.howtoforge.com/tutorial/how-to-configure-a-nfs-server-and-mount-nfs-shares-on-ubuntu-18.04/

Obviously don't use the chown command if it is standing data. I believe symlinks can be made to be honoured

I think my problem still not covered well. Let me explain,

[Server device] When login to Ubuntu as eg: non-root user then other partitions don't mount automatically (not client side nor about NFS). Eg: GUI mode, In nautilus or dolphin, it ask root password when open particular partition then it get mounted or we have to mount manually

After that it appear in media, we can see the path /media/useraccount/partition1/

Next boot this occur again. (means i have to mount required partition again otherwise path invalid) then any solution for that?

How about if you add the NFS to /etc/fstab

Create a mount point for the partition and create an entry for that partition in /etc/fstab. Then it is automatically mounted at boot time.

Is there any GUI tool for nfs-server side? (and client side too) because sometimes i want to stop it and start again during the day
(it's possible to play with cli but gui tool may has many benefits, just show the status, has buttons to start, stop, show ab connected clients etc)

Just SSH in and stop the services if you need to. You can show the status of the service using the same command you stop and start it.

Considering you are asking if there is a GUI, how do you know there will be any benefits if you don't even know if one exists, what it does, what colour it is.. Nothing