"I want to be a singer."
Translation:Şarkıcı olmak isterim.
This is about English grammar vs. Turkish grammar. You need to include an indefinite article in the English sentence but you do not need to do so in Turkish.
So, what is really the difference between
Şarkıcı olmak istiyorum and Şarkıcı olmak isterim?
If I had to take a guess, I'd say the second option sounds more like a permenant wish. But I might also be totally wrong.
I would translate the first as "I want to be a singer" and the 2nd as "I would like to be a singer". So the more permanent/decided option is actually the "istiyorum" one.
In daily speech, the "-r" tense is rarely used in personal wishes; I think the sentence with istiyorum makes for a better standard answer.
It just sounds a bit off. You rarely use "bir" before professions in Turkish. It is putting a lot of stress on the fact that you want to be "A" or just "ONE" singer as opposed to more :)
it is not really wrong but very unnatural. We almost never use "bir" with professions. So it is also very weird to say "ben bir şarkıcıyım" etc