Cannot import from my own jar

So before the screenshot, i've done only: 

-made a 'lib' directory

-put my jar in it

There's my compiled FlexString class in the com.rippl folder, and a manifest file in the manifest folder, which only includes manifest version, because there's no main in the class.

-then in IntellIJ i right-clicked on the jar, chose 'add as library

And after that we are here:

I think its visible what my problem is. The IDE recognizes the class, as it isn't red colored. But i can't import from the jar, auto-completion doesnt offer it, if i write it manually its underlined red. So i get at the compilation the errors, seen down.

Source code of the class:

It's my first time creating maven project, but i think i have problems with java in the first place this time :D

I appreciate any help in the connection of my codes too.

Thanks for any help!