"We have bread."
Could this be my mamy chleb? I just wrote mamy chleb and it worked. Or is it just awkward to say?
Yes, it can be "My mamy chleb", but "my" is just totally redundant, because the form "mamy" makes it perfectly clear what the subject of the sentence is.
Why not "mamy chleba"? Cuz i thought the ending should be -a in a acc. case for the word "chleb"
In Accusative, for masculine singular nouns, it is important whether the noun is animate or inanimate.
If it's animate, the form looks the same as in Genitive. For example "Widzę chłopca / Nie widzę chłopca".
If it's inanimate, the form looks the same as in Nominative. "Chleb jest smaczny / Mamy chleb".
You also have to remember that a lot of food articles, mostly fruit and vegetables, are considered grammatically animate without any particular reason. So the majority of people would also say "Mam pomidora".