Is there any good program i can use with a GUI to lock a folder with a password? CryptKeeper looks good/cool but is it working with Zorin OS? I cant find any package to download and install like .deb
There are many ways you can do this. You can also compress a directory, then encrypt it using the Archive Manager, requiring a password.
On Gnome, the Gnome ENCFS manager may be useful. And, as you pointed out, there is Cryptkeeper.
I see no reason that Cryptkeeper would have problems on Zorin.
I am also not an expert that can provide detailed responses - but a netsearch on the above should help you find plenty of information.
I would suggest checking Cryptomator and see if it works for you. It work around the concept of "vaults" that you create and use as if they were actual directories on your machine, only you can lock/unlock them whenever you want to.