Can someone please explain to me the rule(s) behind czas turning to czasu. If there are any other online sources that you know of too that could help understand Polish grammar that would be great to know!
Mam requires accusative
If a verb is negated accusative changes to genitive
genitive form of czas is czasu
you can look for some often recommended resources here https://www.duolingo.com/topic/922/top
this book http://www.skwierzyna.net/polishgrammar.pdf is good.
Thank you for your comment, it helped me a lot