"I am definitely interested" is correct and usable in written English. You can use it whenever you want to express strong interest in something. For example, "I am definitely interested in taking your music class. Can you tell me more about it?".
"Oh, no, I am definitely interested.
You can see that I am definitely interested in art and museum librarianship, archives just doesn't seem to fit naturally into that mix.
I am definitely interested in the full stack, and the tech that powers these things.
"Andrea has been absolutely brilliant but I've always secretly thought Theresa was the right man, sorry woman, for the job, party must unite blah blah and if you're recording this then I am definitely interested in any jobs that might be going".
"If you can really help with what I am seeking, I am definitely interested in traveling out to meet you," he told the detectives, adding he had purchased a non-refundable ticket to Phoenix, according to police.
I'm really not interested in taking part in a discussion around that but I'm definitely interested in taking part in discussions that are factually and evidence-based," he said.
"So far I haven't seen anything that indicates they want to have a meaningful discussion around this… I'm really not interested in taking part in a discussion around that but I'm definitely interested in taking part in discussions that are factually and evidence-based".
I was definitely interested.
I was definitely interested in the show.
I'm definitely interested in English and being English.
TC: I'm definitely interested in seeing the city.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union