How to show webform as block
Special thanks to Peacog Web Development for their great tutorial .Here is the tip:


  Rather than Drupal 7, Different Block types can be created by admin


so the solution is simple :


Create a new block type using : admin/structure/block/block-content/types
Add a Reference of type Webform to custom block type
remove body if it's inappropriate
modify custom block Manage Display so the form would be rendered as webform 
your new Block type is ready


now to add any new webform as block you, you will need to add new block of type Custom Block and refer to your webform, and that's done.