I know basic coding in Java. How do i get to next level? Where should i start? For building web apps and so

Answer 1

You can start learning java web framework like Spring, or JSF.

Answer 2

For building web pages with Java there are two ways.
The first (maybe simplest) are Java apllets-it means a java programs with own window inside a web page. The second one are servlets - thats means generate web pages on server in Java (simillar as it do php, described here is course).