How to change the styles, if in addition to the style file.css is still bootstrap.min.css?

Hello. I wanted to change the appearance of WordPress template as usual via the style file.css, but the basic styles, as was prescribed in the bootstrap files.css and bootstrap.min.the css I downloaded these files through an ftp Manager, Notepad changed them I need the settings and uploaded back.

But this externally, the website (template) as it was, and remains, no changes have occurred. Tried even to remove the bootstrap files.css and bootstrap.min.css and also the site remains unchanged. How to edit the template styles?

Here on the website, there is a similar question, but I don't understand the answers. Here it is How to edit bootstrap.min.css?
July 2nd 19 at 18:06
2 answers
July 2nd 19 at 18:08
Solution
as usual via the style file.css, but the basic styles, as was prescribed in the bootstrap files.css and bootstrap.min.css

To put style.css code of the website (connection procedure) the code below bootstraps files.

even to remove the bootstrap files.css and bootstrap.min.css and also the site remains unchanged

And you even know what styles there are prescribed? When you delete a file styles are used, styles are bound to leave.

The only thing maybe is some kind of progressive caching, which makes styles even if you delete.
It is necessary to delve into the admin site or the htaccess file.
July 2nd 19 at 18:10
To use sass

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