I have very basic knowledge in JS and C#, and now I'm trying to build my first web app with JS. I want to create a web app which creates a GET request to Coinbase website and takes the current price of Bitcoin, Ethereum and etc. and show it in my web app. Can you provide me a website where i can start with? Thank you.
Coinbase has a maintained API you can use to fetch the data you need. They support various solutions (REST, Websocket, etc.), depending on your requirements.
Resources for getting started with general web development is an entirely different beast. I would suggest Angular's Heroes Tutorial, and from there read up on AJAX or Websockets (for the latter, I suggest socket.io).
Expect 100-250 hours work.