Those cookies from sites to which you've never been are probably tracking cookies, and many different sites place the same ones, so even if you close one window that utilizes them they may respawn because they're still being used by a window that's still open. (What are your cookie settings in Safari > Prefs > Privacy?)
You're gonna hate this, Rita, but I think it's time for you to upgrade to Safari 12, because it's got new security/privacy features that l suspect address your issue...at least in part (because you may, in fact, have some evercookies). If you're wary of it, experiment on your old MBP or on a clone, and see what happens.
As for CleanMyMac X, you got sucked in; there is no free version, only a free d/l, which is a sneaky way of getting you to try it and see "how many times over it's worth the $40/year or $90/one time buy price", so when the "buy it or lose it" screen pops up you'll bite. (Check out MacPaw's website, and see if you see so much as a hint of a free VERSION.)
