ClassSense reads text, so it does best with subjects whose content lives in words and worked steps: the concepts in biology, the reasoning in algebra, the causes in history. It does less well where the content is in pictures, audio, movement or handwriting. Diagrams and equations stored as images do not survive extraction, and practice inside the app is multiple choice.
Each subject page says what that looks like in a real class: what to upload, what the misconceptions tend to be, and what you will still do without it. Whether other languages work is untested, and the language pages are open about that.