Do I need to be good in painting

Try this only if you have good visual design sense. People generalise ux/ui as designing rectangles with Color , but it requires two core skill

1. Good problem solving skill with visual communication
2. Good visual design sense to evaluate what would work and what wouldn’t

nope you don't need to know how to draw or paint for sure.

Not necessary but sketching or drawing skills help in visualisation a bit

Not necessary.