damaged system library

so: I'm a real dummy, to start with. Because I did the one thing that I knew was not to be done, i.e. entering the system library and removing something.

I meant to empty the cache in order to install a new Operating System (I'm still on Yosemite), but looks like I did something else and it turned out that now a lot of things don't work anymore. For instance:

in Safari, when I click the names on the favorites bar, they don't open ;

in Adobe Acrobat when I click to save an open document in a file, it doesn't save it;

the screensaver doesn't see my photos anymore, and so does the desktop;

the line printer driver isn't connected to my iMac anymore;

some app don't work (one of which is very important for my work). And so on.

I suppose that the only good thing to do is installing the OS again (or else to install Sierra and/or High Sierra), but before I do another stupid thing I prefer to ask someone that knows what to do.

Any advice will be very much appreciated.

Thanks

Anita