I have been trying to learn Polish.... But this is such a difficult language. It changes a lot and when I think I am starting to understand then boom it changes again.
How can I improve and how long will it take?
Nie zrezygnuj! Don't quit!
Polish is in fact complicated if you are not used to Slavic languages, but it is so unique and beautiful that all the effort will be worth it! And if you need any help I'm glad to help you even though I'm just learning it too. It may be useful for you because I speak both Portuguese and Spanish, and I assume you speak one of them natively.