r/Hanzi

So I grew up in a Chinese household, so I know a lot of chinese and am completely fluent in speaking, however I can't read nor write(in China i'm what is called a wen mang) and I actually really want to move back to China when I'm older and retire, but also because I need to visit relatives so I want to become fluent again(as I moved to the UK when I was young and at that time I could write and read pretty fluently) but now I pretty much can't so what would be the best way to learn Chinese now? Also I'm sure there are plenty of people with similar experiences so I would like some advice.