Rotting Bathroom, what supplies and how to use them? Help desperately needed 🙏

Came into this new space, and I don’t think roommates ever cleaned bathroom. It may be that dogs used to get bathed in here as well.

What type of materials might I need to clean this? Bleach? A heavy scrubber? Can the plastic lining be saved, or is there too much yellowing / mold / mildew?