I was never learnt how to write and read.
Does that mean you are illiterate? I mean, can you use language, numbers, images, computers, and other basic means to understand, communicate, gain useful knowledge, solve mathematical problems and use the dominant symbol systems of a culture.
What. I said I can't read and write. 
Ok, so you cannot read or write on here, so you cannot understand what I am saying? Well, that is very sad.
Yeah, it is pretty sad. I really wish I could understand what you were writing. 'Tis a shame.
Reading development involves a range of complex language underpinnings including awareness of speech sounds, I am sure you can understand when people talk. I am also sure you can read what I am writing.
Yeah, I can understand what people are saying. I just can't read. I wish literacy was a more focused on topic back in grade school.
Usually, in order to understand a text, it is necessary to understand the spoken language associated with that tex, I guess you are not that bad then, and I hope you continue to practice.