Descartes's solution to the problem of how a thing exists from one moment to the next is that God continually recreates things. You are the same person you were a minute ago, you believe. Surely the present, by its own momentum, is presupposing the future. That is why diagrams lead you into error. The present is to be understood as an outgrowth of the past, only not wholly an outgrowth of the past.
Immaterial things have cogitation.
By this he means not just thinking, but having every form of experience. He says motion is a mode. But having that modal form of experience, motion, he should have made it into a fundamental quality, rather than an accident. Yet he says each substantial thing requires only itself in order to exist. This is a difficulty which cannot be solved in terms of his presuppositions.