Help please marble

Hi everyone,

I recently got a job cleaning the marble stairs in my building. I tried using a bit of Mistolin to remove some stains, but the next day everything turned yellow and the white streaks became visible. In fact, the stains now look even more noticeable along with these yellow marks.

Today I tried cleaning it with alcohol, baking soda, and detergent, but nothing worked. It’s my first week on the job and I’m already really stressed about it because of the €60 — it’s even been keeping me from sleeping.

To be honest, I’ve also been avoiding the people in the building because I’m embarrassed about the situation.

Does anyone know how to fix marble stains like this or remove yellow marks from marble? I’d really appreciate any advice.