I keep telling my child the same thing, but they don't understand.

A situation that takes patience; being tired is natural. In common: rather than "deliberately not listening," it's often that understanding is genuinely still hard, or the way it's conveyed doesn't fit. Showing with pictures, real objects, and demonstration—not just words—conveying one thing at a time, and matching the same words and steps make it get through better. Empathizing with the feelings of a child who can't is very hard, but patiently, gently, and carefully repeating the explanation is the basic approach. A guide: "does the way I convey it suit the child?" "am I asking too much at once?" Its not getting through isn't your lack of effort. Changing how you convey it can open things up.