Installing Dolibarr on my hosting (ionos) in a Subdomain

Well, I’m not an programmer, I am still learning.
And I’m doing this as a favor for this is not my core business, so I’m not making any money of it.
But I do want to make it possible for him because I do believe this is a great CMR sollution.

I would very much appreciate some pointers in what I’m doing wrong.

Thank you in advance for any help you can give me.