some: du (m) or de la (f)
Je mange du fromage. I’m eating (some) cheese. Tu manges de la salade. Il mange du pain. Elle mange du chocolat. Elle mange du gâteau. |
Nous mangeons de la viande. We’re eating meat. Vous mangez du poisson. Ils mangent de la pizza. Elles mangent du dessert. Elle adore le gâteau. |
You’re right. It’s impossible to tell the difference from the way it sounds. It’s only from the context of the conversation that you would be able to tell.
“Ils mangent” sounds almost exactly the same as “Il mange” and the feminine form too. Besides the writing, how will someone be able to tell the difference when I say, they are eating or he is eating?