Start by doing some real research, instead of just looking at youtube videos: your question is tagged with "C" and "Java" - neither of which is used to construct a website!
It's not really possible to say "learn this and you'll be set up for website coding" because it's going to depend on what kind of website you want: a blog would need one set of skills, a shop a very different set, and a site like this yet another.
Sites can be built in HTML; or HTML and Javascript; CSS; or they can be constructed in a client server fashion using a back-end language such as C#, VB, PHP, etc. They can also involve front end packages like nodeJs, Drupal, or dozens of others. Many (if not all) need some solid interaction with databases, so SQL, or MySql skills are also necessary to a greater or lesser extent.
I'd suggest you start with HTML - it's the basic "building block" of the internet no matter how bad it may be (and it's pretty bad by modern standards). W3Schools have a
HTML Tutorial[
^] which will teach you to create a basic (not really interactive) website and you can start to decide from there which direction you need to go.