Would "Saya tidak bisa makan kacang" be an appropriate way to say I'm allergic to peanuts?
Yes, right. You can say "Saya tidak bisa makan kacang karena saya alergi kacang"...
Isnt using tidak and bisa redundant?
Absolutely not. "Bisa" means "can" or "be able". "Tidak" just negates it. So "tidak bisa" means "be not able" or "cannot".
Sometimes dia is translated as she and sometimes as he....what is correct?
Indonesian only has one word for both "she" and "he": "dia". So guess which is the right one! :))
Dia is he or she
I said He, why is that not accepted as Dia can mean he or she