or depending on how is the sentence structure for the most part?
Nouns, pronouns and adjectives change their endings to show their relationship to other words in the sentence.
If you haven't found out yet, polish nouns have different forms for expressing grammatical case, related to the function of a noun in a sentence. A polish noun also has one of 3 genders, masculine, female or neuter. The 7 cases are , nominative, genitive, dative, accusative, instrumental, locative, and vocative in both singular and plural.
So a noun like sklep ( shop/store) may look like this in case form..
and their plurals, sklepy,sklepów, sklepom, sklepy,sklepami, sklepach and sklepy.
If you have just started to learn polish, then this may be a little too advanced for you but there is no need to rush. I would advise you to start of, learning the letters of the alphabet and then the spelling and grammar rules with them. Learn the basic phrases like hello, goodbye, thank you , I would like a coffee etc, build up your vocabulary then later on, get to grips with the 7 cases.
Above all take your time and have patience, after all you are trying to learn one of the top five hardest languages :)