How to clean the green dirt formed on the bathtub

Vinegar, toothpaste, etc. are too weak.

The green dirt you mentioned may be moldy. First, apply a strong acidic toilet cleaner like the one used to clean toilets on it, and then brush it vigorously with a brush. Finally, you can mix Velox household disinfectant in a certain proportion and then soak and scrub the entire bathtub to prevent similar stains from growing in the future.