Unfortunately nothing functions. If I put the datadir to my ext SSD, it Bitcoin Core still starts from the beginning with downloading.
If I try to do it through terminal, then I get this output:
ln: illegal option -- /
usage: ln [-s [-F] | -L | -P] [-f | -i] [-hnv] source_file [target_file]
       ln [-s [-F] | -L | -P] [-f | -i] [-hnv] source_file ... target_dir
       link source_file target_file

So I don't what to do. Probably have to download the entire blockchain again.