How do I get of mold out of my shower walls ?

Have you tried using bleach? You might have to let it sit for a little while before you rinse.

First dry everything thoroughly.

Then as Auggie suggested. Bleach, bleach and more bleach. You have to kill the lingering mold spores.

If the problem keeps on recurring, you may want to consider re-painting the bathroom with mildew-resistant paint.

Another thing to get in the habit of doing is opening the bathroom window(s) for awhile after showering to allow adequate drying out. Dampness is the friend of mold.

I use Tilex mildew and mold spray. I gets rid of the mold on the walls really fast. Since usually I get mold on the caulking around the tub, I squeeze a line of soft scrub around the entire tub and let it dry. It kills the mold completely.

All good suggestions, and also double check that you have ventilation in the bathroom. Good ventilation will help to prevent or minimize mold growth.

I agree with @YARNLADY; Tilex works great. One additional tip for using it; spray it on, leave it for 15 minutes, then come back and sponge it off. The mold comes off like a dream.