Hi @sumitrana9910,
Check this video https://www.youtube.com/watch?v=WiYNrx1Grak I have not used the synching from host to guest OS using the Virtualbox.
But I have used vagrant and it works smoothly on all the devices. I will suggest you to destroy ubuntu 14.04 and install 16.04 or 18.04 box and you can continue the experiment and the best part of vagrant is you can easily configure to synch the folder between from Host Os to guest OS.
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Use the below command to destroy the older ubuntu 14.04
https://www.vagrantup.com/docs/cli/destroy
(Do not forget to remove the Vagrant file from the folder otherwise you will not be able to install the new box on the same folder. ) -
Use the below command for installing the ubuntu 16.04
vagrant init ubuntu/xenial64
vagrant up