How Long Should I Wait to Re-dye My Hair?

I had dark brown very curly hair and went to a professional hair salon to get blonde highlights and my hair got completely destroyed. First, it was bleached and then toned. But they did something wrong and my hair was grayish purple. They tried to remove the color and dye it with semi-permanent color 3x, but it still didn't work. Now my curls are almost gone and there is about 5 different colors in my hair. I want to re-dye it back to my dark brown color, how long should I wait? The photo is my hair now.

Please help :(