What code should i learn to make my website?

[☕JavaME☕]

Client side:
HTML - Designing the structure of the Web Page.
     (How the website basically looks)
CSS - Managing the styles
     (Making the website more "fancy looking")
JS -  Adding the dynamics to the Web Page
     (What happens when you click/edit something, etc...)

Server side:
PHP - Used to make the Web Page interact with the server
      (Log in/Sign in/Upload/Download)
SQL - Used for managing Data Bases (Like user data base)


If you want to Sign in/Log in/Upload, then you would have to use PHP and SQL.
You need PHP to make Sign in/Log in system and for uploading the files to the server
And you need SQL to manage the user data base.