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、很"，用来加强语气。 much 在这里也是副词，意思是"很大程度上"。 pretty much 是一个固定搭配的副词短语，意思是"几乎、差不多"，表示接近完全的程度。