The term most people here would use for your job is “contractor”, not “consultant.”
A consultant, in most people’s minds, is someone they would consult with, who would tell them what to do, in an advisory capacity; not someone who would actually do any kind of work. (In other words, a management consultant.)
The only people who use the term differently are consulting firms themselves, because they think “consultant” sounds fancier (and worth paying more for!) than “contractor.”
Maybe you're right, my language has no such distinction (Italian) it's one term.
wouldn't that just be: "subappaltatore - una persona incaricata di svolgere un lavoro"?
Subappaltatore means subcontractor. When a contractor hires a second contractor to do part of, or all, the work.
But appaltatore isn't strictly a contractor in the generic term either, its mostly related to win a "gara d'appalto", so winning a tender.