Another tip about Polish that will help you with learning:
Many polish slang words were created by shortening popular phrases.
1) to say 'hi' you can use the word 'siema', which comes from a phrase 'Jak się masz?'
2) to say 'all right' you can use 'wporzo', which comes from the phrase 'W porządku.'
3) to say 'see you later' you can use 'nara' which comes from 'Na razie!'