Hey Kumar, did you try googling the search terms: "learn web development" "crash course web development" or "development 101"? I find most of the in demand skills nowadays can be learnt through googling phrases like that. i'm sure they will lead you to some sites with courses or blogs on the topic, where you can easily learn and expand your skill set :D
As for your second question: "what do i charge for web design". well that depends. i work with 3 web designers regularly (and can design websites myself too, although i choose to focus more on graphic design and illustration), prices typically range from $150 to $ 5000 for a website. It mostly depends on how many pages and functions the client wants on his site. for simple sites, that can easily be built using Wordpress templates i'd go with a price of about $150 - $300. anything more complex than that requiring back end development, and lots of coding would fall in the thousands.
Graphics design is huge. I have seen people getting paid tons of money for a single project. Depending on what you can do, you should definitely check out sites like Upwork and offer your gig there, for starters. Fiverr is a good option too, although you would be working at much lower pay in the beginning.