"I would not eat this."
Translation:Nie zjadłbym tego.
It kinda depends on how we interpret it, I think. "Nie jadłbym tego" is like "If my grandma wanted to serve me mushrooms once per week, I wouldn't eat it" and "Nie zjadłbym tego"... about a specific occasion when she served mushrooms. Both make sense. Added the imperfective forms.
Well, it sounds very weird, and if I had to guess the meaning, I'd guess "It is not this that I would eat".
But even this should rather be "Nie to bym zjadł (for a man)/zjadła (for a woman)". Firstly, in such a sentence you would negate "it" and not "eating it", and then, "zjadł(a) bym" looks a lot better to me at the end of the sentence. Not sure if it is applicable for every sentence, but I would write it like that here.
Firstly, the correct form would be "Nie byłbym tego zjadł".
Secondly, this is a sample of illusory conditional mode in Polish, something that is a pretty high-grade stuff even for Poles, as it comes from plusquamperfectum (czas zaprzeszły). As far as I know, czas zaprzeszły is not taught in this course, and in contemporary Polish this tense is commonly used only for 2 verbs: "powinien" and "winien".
Thirdly, (and sorry, from this point on, it is only my interpretation), this phrase does not make any sense alone, because it may be only a part of an (illusory) conditional phrase, and only the conditional part thereof, with the word "gdybym" implied (it is feasible), and with the resulting part missing - as the other way round it does not make any sense (at least to me); maybe someone could correct me if I am wrong.