How to use bootstrap css for form inside the popover?

Hi, I am rashid developer of We have a multisite installation. We are using popover( Pop Up) plugin to display gravity form.
Our gravity form is using bootstrap form for design.

But problem is form inside the popover is not using bootstrap css class. All classes from bootstrap is overwritten.

I tried many ways like added bootstrap.css at footer. Also tried by adding bootstrap.css at the end of <head> tag.

I would appreciate your help for getting the solution, how can I use bootstrap.css for popover.
Please check the form here: