You will find below different resources available online that you can use to study the Polish language on your own.
I have kept the number of resources listed here to a minimum; beyond a few altogether indispensable ones (such as SJP and a dictionary), the most important ingredients to your success are your patient analysis of the Polish before you to infer patterns and your willingness to persevere across not weeks or months but the many years — the Bible in Polish (see below) will sustain you for a lifetime. Anyone under the misconception that Polish can be learnt in three months, as certain ‘modern’ language methods or online personalities may lead one to believe, will be in for a rude awakening indeed.
WSJP and PWN are monolingual Polish dictionaries available for consultation online. As for online bilingual dictionaries, none are satisfying but can include: PONS, Cambridge, WordReference, bab.la, Translatica.
The monolingual WSJP and PWN dictionaries are decent, but you will of course have to understand Polish to use them. I do not find any of the free online bilingual dictionaries particularly useful beyond general vocabulary and prefer to use the printed Great Polish-English English-Polish Dictionary (Wielki słownik polsko-angielski angielsko-polski) by Jan Stanisławski for my work on this website; I use any of a two-volumed version from the 1960s, a four-volumed version from the 1970s and a four-volumed version from the 1980s. If you use the notes that I have published here to learn Polish, you can consult the vocabulary lists that I have prepared and inserted into the posts.
How to find words in a Polish dictionary: if you encountered łokci in your readings and went to look it up in the dictionary, you would not find it. This is because łokci is an inflected form. Using SJP, you will trace inflected forms of words back to their base, dictionary-heading form. By entering łokci into the SJP search field, you will discover that the word in question is łokieć; from there, you can now perform a dictionary search. You can enter any class of word into the SJP search field.
Polish grammar and pronunciation
Learn the Polish alphabet and how to pronounce the letters on culture.pl or Wikipedia. To consult declensions, try odmiana.net, or Wikisłownik and Wiktionary (if you cannot find what you are looking for in the one wiki, you may yet find it in the other). A certain number of declensions are available here through the notes on my site; I am always adding new declensions and aim to have presented a decent number of them with time. For verb conjugations, try Cooljugator, bab.la, Verbix.
To learn the grammar of Polish itself, I recommend choosing a text (preferably one for which you are able to obtain both a Polish version and a version in your language) and analysing the language of it on your own; if you work your way through the text of the Bible (see below), the grammar of Polish will progressively reveal itself to you and you will not remain perpetually at a beginner’s level because you will have a great deal of material with which to work across the years.
Reading and listening in Polish
On this very website, you can study Polish through the Bible. Consult the vocabulary and grammar notes as you work your way through the chapters. Using the Biblia Tysiąclecia to learn the Polish language comes with my highest recommendation. The range of language you will learn is nothing short of phenomenal; you will not be disappointed. Begin your study with Rdz 1, which is the first chapter of the book of Genesis. If you have chosen to study Polish by this method, you can listen to everything that you have studied: the entire text of the Bible has been recorded.
And why not — when you need a little break from Polish, you can start getting your Friulian underway.