As far as I know 저(I) isn't/cannot be used in a this kind of sentences where there is no honorifics. Instead 나 should be used. Am I right?
You're right as far as I know. It's a foreigner mistake. I should know since I used to do that.
It really has to do with honorific phrasing. 나 is just a little less respectful even though you are talking about yourself.