To fix this you need at least Samba 4.3, they did some cool stuff in vfs_fruit.
Then you add this in your share in the samba config.
vfs objects = catia fruit streams_xattr
fruit:resource = file
fruit:metadata = netatalk
fruit:locking = netatalk
fruit:encoding = native
Now folders and filenames should look normal, and large folders should open up faster.