I am a Web Developer and I know React JS & Angular. Can I use languages technologies to make websites?

React and Angular are JavaScript frameworks which is used often for web development. JavaScript usually adds functionality to sites. So you can implement JavaScript in your website only when the basic structure of the website are built with languages like HTML and CSS. HTML makes the basic structure of the site while CSS is used to make the site more attractive / to design the site / make the site responsive.

HTML & CSS are way more easy to learn compared to JavaScript. As you know about JavaScript so I might consider that you have the knowledge of HTML and CSS. If you don't yet know about HTML & CSS, I would strongly recommend you to learn them first because these are the fundamental languages for web-development.

As you know JavaScript so I am pretty much sure to consider this that you will be able to know HTML and CSS easily within a few weeks / months. However it is not only limited to make the front end of the website to make it live. you should also learn backend languages like PHP & MySQL to manage your databases or else mini great functionalities will be missing from your site.