After knowing the required languages, how to build a dynamic website?

It is better to use an open source platform such as Joomla, Word Press ar whatever. They save a lot of time.

If you decided to reinventing the wheel, you need to do the following:

1- Design the website interface using Photoshop or any similar software

2- Convert your design into HTML code. Using div design is preferred over table design

3- Design the database tables

4- Write the source code to store and retrieve data from database, handle user request and populate the HTML template generated in step2

This is a quick brief of the road map.

A dynamic website uses a server-side technology to generate the content you see on the site's pages. Using a server-side technology opens up a wide range of possibilities: e-commerce, customer management systems, direct user feedback, and adding a search form to your site.