"Do you really want to become a politician?"
Translation:Gerçekten politikacı olmak istiyor musun?
yes, it would be wrong if an english sentence didnt have "a" . As in; Do you really want to be teacher?- absolutely wrong
trust me, I am Turkish. It is much more natural and common to say Gerçekten politikacı olmak istiyor musun? than Gerçekten BİR politikacı olmak istiyor musun?.
Just like almost nobody says "Ben bir doktorum", but they would rather say "Ben doktorum".
You HAVE to use "bir" in such a sentence to be grammatically correct. This is especially very important if you are writing a formal essay or a petition.
"Ben bir doktorum." The only thing you can understand from this sentence is that the speaker is a doctor. İt is specific.
"Ben doktorum." Which doctor? Are you A doctor or are you THE doctor? İt is unspecific. Might confuse people.