Depends on the man, actually...I've met more than a few ...
I would argue ...
why dzieckiem instead of dziecko?
Objects after the verbs jestem, jesteś, jest, jesteśmy, jesteście, są, etc., decline to the instrumental case.
Welcome to Polish cases :)
Polish is so hard and i have two months to learn enough to be able to speak it and understand what polish people say....
I'm sorry to say this, but I don't think 2 months are enough, unless you are some kind of language genious and spend 12 hours a day learning Polish.
Im actually doing that since two days ago xD
why is the translation wrong if I did not use an 'a'? I answered 'Man is not a child'.
Because "man" means "mankind." "A man" is just mężczyzna
Why is dzieckiem in narzędnik? Wouldn't its negation cause it to be dopełniacz?
Not all cases behave like that. Instrumental stays instrumental.
Wrote mam instead of man and my answer was wrong?
What's the question? You didn't write the correct word. I understand it was just a typo, but we have no power over what gets 'accepted with a typo' and what is just rejected.
so basically after jest or jestem I have to chose the extended version of the word?
You have to use the instrumental case of the noun and its adjectives, after jestem/jesteś/jest/jesteśmy/jesteście/są.
Different cases are not extended versions of a word. They're just cases. Some cases shorten the word.