Bath Enclosure Tub Help Cleaning A Bath Tub....?

Help cleaning a bath tub....? - bath enclosure tub

My mother has just gotten married and now lives in a house that people lived in the 2 years already.
The bathroom and the land is bad .. they are so dirty. She tried to wash herself, but without success. Only a small drop ... She also has a back injury and can not wash much.
Replacement is not an option yet ...
Does anybody know of some strong cleaning agents that help to ... ?
Thank you ..