Use a rag to scrub with some water. If the color is dark and large, it is recommended to use the same color paint to brush the painted area.

the easiest way is to polish it and repaint it. If the location is available, you can hang a small ornament to cover it.

If it is oily handwriting, you only need to sell a water-based pen to draw along the original handwriting on the wall, so that the original oily handwriting will react with the newly drawn water-based handwriting, which will naturally be particularly easy to remove, and then gently wipe the original oily handwriting with a semi-dry towel.