There’s some excellent reference material at
polish-translators.com/grammar. The tables of noun- and adjective-declensions will be useful in due course but they will be very daunting at first sight.
I would suggest that you start by concentrating on the difference in pronunciation between the Polish consonants ¶ æ ¼ d¼ and sz cz ¿ d¿. When you first hear them, the first four will probably sound like the second four, but to Polish speakers they are entirely different! What you should avoid is pronouncing either set like the English sh ch zh (as in pleasure) and j as in jam. Get this right at the beginning and you will save yourself trouble later.
I attach a diagram of the tongue position for ¶ æ ¼ d¼.
 polish_si.png
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