Why is it slow to rotate the mobile menu on the site from the phone?

Question

css

Good afternoon, please tell me, I’m making a website header, everything is fine on the computer in the mobile version, but when you enter the menu from the phone, it terribly slows down when expanding. What could be the reason for this and how to fix it? Site on Bootstrap.
In order not to be unfounded, a link to the site

Answer 1

Probably with the quality of the phone. I think the effect can be repeated on any weak laptop, especially toshiba.