Its okay it might be hard to speak german because I learn it and it gets hard. But if you make mistakes you can learn from it and when you see that same question. When u got it wrong and you see the answer you caan memorize that answer and use it for the same question and you should get it right. But if you didnt just keep trying. Thats my advice
"The", "this" and "that" are all examples of definite articles. Definite articles introduce a SPECIFIC noun. "A" and "an" are examples of indefinite articles. Indefinite articles introduce NON-SPECIFIC nouns. "A woman" (non-specific noun) is eating (action verb) the rice (specific noun).
When is isst 'is eating" and when is it "eating'?
I don't think isst can ever be translated just "eating", without "is".
sie isst can mean "she is eating" (right now) or it can mean "she eats" (habitually, repeatedly, in general, ...) but never "she eating" (which is not correct English).
Usually, context will make it clear whether a given action is taking place right now or whether it's a repeated action, but in a sentence out of context such as here on Duolingo, either translation ("is eating" or "eats") is possible.