How to open a new form in a block without reloading whole page? I am using Webform with ajax mode. I have added the Webform in block so as only the block is refreshed instead of whole page, it's working fine. 

All I want to do is open new form after getting confirmation message without reloading whole page.

How can I do so?
You need to set the "Redirection Location" to "No redirect (reload current page)" in actual webform settings (/node/x/configure). This will show the confirmation message in block without reloading and provide a link "Go back to form" which will reload your form by ajax.