how to increase website speed

Increasing you offer for sure it will work :D

first analyze your site with any app *rec(Gtmetrix)
next :
optimize your images (decrease all image size under 100kb)
Use cache plugins if u have wp site use (wp-rocket)
increase your host performance

Don't waste your time guessing or trying things.

If selfhosted on Wordpress, disable your plugins, get a google search console audit and do as they say