Nodding along when you don’t understand just postpones the moment you get exposed.

Nodding buys you about ten minutes. It protects you from looking lost in front of the room, and it guarantees you will be lost again next lesson, on top of the same gap plus whatever got built on it. Confusion compounds quietly while the nodding keeps everything looking fine.

Ask the question at the moment it appears, even in a clumsy form. Name which word or which step you lost, rather than saying you do not get it. If asking in front of people is too much right now, ask one classmate before the next lesson.