How do I remove grease stains on the walls?

Are the walls painted or tiled or what? Use some elbow grease, a knobby washrag, and Dawn soap and hot water, or you can use a mixture of baking soda and hot water, and put on the rag, and gently scrub -again some elbow grease, and patience- and rinse your rag well, til wall is clean. Then make a wipe down a habit after each use of the stove, - like when you wash your dishes, wipe toaster, stove, microwave etc., -that way, grease stays away!!!! and you won't have a big cleaning job, or if you do, it won't be hard to clean, or take very long to do!

If you can stand the smell ammonia works well. When we bought our house the hood above the stove was dripping with grease, and that’s what I used.

Use vegetable oil on them. Put on and let sit several hours repeat if necessary

White vinegar, wash the walls down.

Okay I will try that thanks.