"I have water."
Ja mam = I have
in Polish we ussually skip pronouns when they are not needed - so we skip I you (sing) we, you(pl) as subjects of sentence and also he/she/it/they if context is clear or in past tense. If you not skip those pronouns you add extra significance to the fact that it is you who has water.
If you are going from English to Polish, you can generally drop definite and indefinite articles (again, this isn't a formal/informal thing; some languages just don't use them the way English does--whereas some, like French, use them much more often...).
However, in Polish-> English exercises, Duo still requires them when necessary to a grammatical English result, so you can't just not think about them at all...
I get what you mean bud, but Jellei has mentioned using certain articles in formal speech now and again. As a total noob to this language (although not to French - RIP), I want to make sure I get the main principles engrained in my head so that I have the knowledge available when needed, instead of learning it when I need it, you see? Cheers for the quick reply
Wait... aren't you mixing "articles" and "pronouns"? There are no articles (equivalents to "a/an/the") in Polish.
Pronouns (I, you, he, they etc.) can definitely be omitted every time for 1st and 2nd person, unless you want to emphasize "It was YOU who did it! (and not me)", and 3rd person can be omitted when you think the context makes it clear enough who the subject is. If you start telling a story about Mary, you won't suddenly start the 3rd sentence of your story with "Ona", we already know that Mary's the subject. And frankly, in real speech usually either the context will make it obvious, or you will use some other, more speficic phrase ("the doctors", "Frank", or "Ms. Smith") to refer to the subject.