You can pretty much tell your mother any problem you have and she'll try her best to help you out.

pretty 在这里是副词，意思是"相当、在很大程度上"，用来修饰形容词或副词。 much 也是副词，意思是"很大程度上、几乎"。 pretty much 是一个固定搭配的副词短语，意思是"几乎、差不多"，用来强调程度或范围。