I would really like more notes: I realise this is beta and I'm enjoying it, but a clear briefing about the various case endings when they come up would be helpful.
I wonder if "I'm tired" should be acceptable. Poles often say "Nie mam sily" where English speakers would just say they're tired (physically). Like at the end of a hard workout.
It could have pretty much the same meaning (but the Polish sentence more likely means that I just don't have strength right now), but it's a different sentence: Jestem [słaby/słaba].
I know this isn't an English course but we would need a qualifier in this sentence to make it sound right eg "I do not have the strength" or "I don't have any strength" or "I don't have enough strength"