How to modify default login page using theme? Version: Drupal 8.7.x

Currently, I am using a subtheme of the Bootstrap theme and I want to override the default login page because the interface doesn't look good. I was hoping to override the template file in Bootstrap theme responsible for login but there was no file with familiar name in the theme folder. Maybe Bootstrap inherited the login file as well? Then I created a file named page--user--login.html.twig and put that in my subtheme folder but there was no change in the login page. Maybe the file name is supposed to be different or it is something else entirely.
Go to 


  web/sites/default/services.yml


and change the debug value from false to true 

debug: true




You will get file name suggestions like shown in the image, u should use the same names.

Also, was your sub-theme succesfully installed?
Is the sub-theme under this path ? `


  themes/custom/myproject_bootstrap_subtheme


`