Hi @Sumaira , I know it's an old thread, but in case you haven't resolved yet here is an idea to your issue:
you can embed your portal as an iframe, you will need to set the x-iframe options
also would be ideal to have your entity form / web page place in a custom Page Template, so you can hide the header/footer
this post might help: https://colinvermander.com/2016/12/27/using-your-dynamics-365-portal-in-an-iframe/
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