However: The suggested asnswer " I am 1 engineer" is just as wrong as omitting the "an". My2cents
Why is "I am engineer" incorrect?
because that's not correct English. In portuguese you can leave out the "um/uma" but in English you don't leave out the a/an
So there should be article in portugal sentance?
No, it is not usual to include the indefinite article for professions and occupations.
When can you omit articles?
Whenever you are using it for "adjective-like" purposes in Portuguese.
Professions fit that perfectly.
I have no idea how to pronounce engenheiro. Is it a 'j' or 'g' sound?
en jee nairo (pronunciation)
En je nheiro (NH)
Just like in English, the Portuguese g has a hard sound before a, o and u, and a soft sound before e and i. T and d also have hard and soft sounds in Portuguese, though not in English.