what list of things do you need to know to become fluent in a language

1. culture and origin behind the language

2. pronunciation & alphabet. know the letters, know how words are pronounced or everything you learn means nothing

3. pronouns and modifiers (such as plural endings)

4. everyday words, greetings, determiners (such as 'the') and conjunctions, signs, buildings, etc. you should be able to respond properly no matter what someone says

5. grammar, especially for those in Polish and some other European languages

6. slang

hello, please, thank you, and where is the toilet

Speak the language as often as you can and ideally live in the country of the language.