I’ve tried it and it works. I did it with downgrader which can also upgrade ???
I used the package lib32-nvidia-utils-384.69-1 from ALA which was for me #1.
$ downgrader lib32-nvidia-utils
Downgrader can be downloaded by the way with yaourt.
$ yaourt -S downgrader
For me it works now. Hopefully this is the right way. I do not want to have problems in the future.