How to help my depressed friend clean their room

TW FOR MOLDI FOOD .My friend is depressed and I've been trying to get them to let me help them clean their room for a bit now. last December they finally said yes and they let me come over to their house and it was worse then I was expecting. To describe it they have a big room and couldn't see the floor bc there where clothes and rubbish everywhere and modi food the bed frame was broken and on the floor so they had food that had gone off near where they sleep bc of this they always have the widow open so it was freezing we where able to clean the floor from the door to the bed and most of the moldi food that we could see but we had to stop bc i felt sick bc the mold and it was late .now its been a few months its gotten bad again and I want to go back to their's more prepared to get the job done but they won't let me come over to help idk what happened in that time but they say it'll just end up mesy again ive told them Idc if it end up mesy again bc their my best friend and have been there for my worst times so its only right I do the same and that everyone deserves to have a clean room ive also told them it'll make them feel better and help take stress off but they won't listen.

Dose anyone have advice for cleaning in general but ESPECIALLY THE MOLD that's my absolute main priority is getting that stuff out ive also asked if we could maybe get outside help from ppl like her mum but she said absolutely not bc she's just shame them so its just me and them

Also I'm sorry for bad writing I'm dyslexic af

Any and all help would be fantastic their my best friend and I'm seriously worried for them