Does bootstrap3 affect page loading time?

Question

css

Hello!
People, such a question. The employer says that when using bootstrap3, the download speed will increase significantly. Is this assumption correct? I found an answer, which says that, on the contrary, like any framework, it slows down the download, but I would like your opinion. And one more thing: do you need a bootstrap if the site is not adaptive? Here the employer rested, use the bootstrap and that's it. But what for if the sites (examples below) do not adapt?
Second question. If the site takes a long time to load, can there be reasons in the layout? The layout is ordinary, nothing superfluous, nothing heaped up. Here are examples:
1. designer-curtains.rf
2. restaurant- nomad.rf
Pictures are saved in JPEG, quality 60.
PS The design is not mine, I'm not a designer.

Answer 1

https://developers.google.com/speed/pagespeed/insi...
more problems from unoptimized images

Answer 2

Yes, bootstrap is probably redundant. But after I discovered uncss, I stopped worrying about this topic. It cuts out everything that is not needed
. Now, during development, my css is 350kb, after uncss, mqpacker and minification it is 32kb. So it goes.
ZY Be careful with bootstrap js components. Their styles are constantly cut off and you have to add them to ignore.
And yes, pictures load much more significantly.