How to make my website dynamically resize elements

Im relatively new to web development working on creating a website using React JS.

Im really not able to figure out how I can make the elements on the website resize or arrange themselves nicely when the window gets resized, or appear like when viewed from a mobile device.

Like all the elements adjust themselves based on vh and vw when the window size decreases/increases diagonally, however if the vh stays the same and vw changes, everything ends up all over the place.

Are there any plugins or anything ReactStrap related that can help me achieve this dynamic resizing and fitting? OR should i use tools like wordpress which seem to automatically take care of this issue rather than me manually writing all the HTML and CSS for the website.

Thank you