,my sidebar does not contain my saved folders anymore and I cant add any

As Old Toad requested, please post screenshot(s) of your sidebar.

Also: maybe your "Favorites" section is simply twirled closed.

Hover the cursor near the word "Favorites" in the sidebar. Either a rightward ">" or a downward "V" will appear.

Which one? If you see ">", click it and it will disclose all your favorites - including your saved searches.

Please read the following user tip and restate your question/problem in detail: 

     Writing an Effective Apple Support Communities Question - Apple Community

Add a screenshot of you sidebar from top to bottom (may take more than 1).

Have you tried launching your library with the Option+Command keys held down to repair/restore the library?