help with javascript/boostrap logic

I don’t understand the logic in this. Please anyone shed some light here.

I experience some modals not opening and there’s talk that it’s because 2 instances of jquery are launched. The firs thing I don’t understand is: if plugins need javascripts/jquery/boostrap to function, wouldn’t they stop working if I disable those scripts?

Secondly, whenever I look at the inspector console, there’s always one particular plugin listed with /bootstrap/bootstrap.min.css. So I think that I should disable/tweak that very plugin. And here comes the strange thing: if I disable this plugin many parts of my site break (like modals, footer, sidgets, etc.). And I’m like: it should be the opposite, it shouldn’t break the site if I disable it! This plugins acts as a corner-stone to the whole website, but it came after not before the website.

I’m no developer, right, but this is really confusing me.