i can't write code only but i can't also understand what i read :)

I dunno. While I haven't smoked weed while working at all since leaving uni, my uni final year project - an augmented reality headset which got a reasonable bunch of publicity and was professionally rebuilt after I left uni - was conceptualized, designed, built and programmed while myself and my project partner were high (over the space of about 3 months). My project partner is now one of the leading researchers in a specific area (which I won't mention to help protect his anonymity) and still does a lot of his work high.

Of course, this in no way means that others should do the same and what worked for me then and what works for this guy now probably won't work for everyone. I certainly wouldn't do it while working on something important now.

Sure, we can all find exceptions. I would imagine it works for some. When it comes to giving anonymous advice on the internet however, saying "don't smoke weed when you're trying to work" seems like good advice.