Polish numbers are ridiculously complex. As an English speaker I really don't see the need for all the levels of complexity.
And so as usual with most these grammar essays/articles I've have only taken a broad outline or approach which has helped me.
If you remember nothing else, this is helpful.
Start by learning the ordinal numbers from one to ten, followed by the numbers from one to twenty.
These numbers are in the nominative case. This is important as the endings of Polish numbers can and do change, as can the noun being followed.
Polish nouns following numbers less than four are in the plural, as can be seen in these examples from the Polish sentences.
But, the numbers (below five) behave like adjectives, that is they decline and agree with the noun (to some extent).
Instead of trying to commit various number tables to memory, just be aware that the numbers decline depending on the case and gender (including a distinction between male animate and inanimate objects).
| I have two children | Mam dwoje dzieci |
| I have two cats | Mam dwa koty |
| I went for two weeks | Pojechałem na dwa tygodnie |
| Two days ago I went to the bakery | Dwa dni temu byłem w piekarni |
| My flat has two rooms | Moje mieszkanie ma dwa pokoje |
| He works three days a week | Pracuje trzy dni w tygodniu |
| I've been a teacher for three years' | Jestem nauczycielem od trzech lat |
| I go swimming three times a week | Chodzę popływać trzy razy w tygodniu |
| I went to Poland three years ago | Byłem w Polsce trzy lata temu |
Set phrases such as dwa dni temu and na dwa tygodni occur again and again in spoken language and so you soon remember them.
This is obviously useful as is, but also because if you are aware that number behave like adjectives, you start to see and become familiar with the patterns.
Polish nouns following numbers greater than four are in the genitive plural.
| one cat | jeden kot |
| eight cats | osiem kotów |
Polish numerals when used with male nouns have a special form with a different ending which is u.
| Number | non male | male |
| five | pięć | pięćiu |
| six | sześć | sześciu |
| seven | siedem | siedmiu |
| eight | osiem | ośmiu |