Misunderstandings, colloquialisms, wrong words and false friends: 12
DARIA: Do you know anyone who knows something about fixing the problems in the bathroom?
ROBERT: You can ask me. I’m a professionalist.
I don't know if this is a common problem in other languages, but here in Poland there is this thing about adding the suffix -ist onto the end of nouns that describes the role that people have. This is not only (but usually) in work, but also in other activities.
Okay, somebody who works in journalism is a journalist; in physics, a physicist; somebody who rides a bike is a cyclist; if someone practises communism, they are a communist; a piano player is a pianist... and so on. You get the idea, although this does not apply to all professions and activities. Somebody who is good at plumbing is not a plumbingist (they are a plumber), and a football player is a footballer, not a footballist. The suffix -er is also used.
So what is a professionalist? Or maybe it should be a professionaller? Is it someone who is a professional professional? That is how such a word could be defined - if it existed of course.
I think Robert wants to make it clear that he is very good at fixing bathroom problems. He may be an expert at plumbing (which would be a plumber, not a plumberist), or he is able to fix things to something like a professional standard. The word professional is often used as an adjective, and so doesn't change. When it is used as a noun, this is normally part of a noun phrase that includes the adjective (professional) and the noun (plumber), but as the context is clear - here, we know he is talking about plumbing - the noun is dropped, often when the person is not actually qualified to do the job, but is still able to perform the task.
So Robert describes himself as a professional [plumber].