How to show language with it's flags.

I got your full meaning. I have this article, you can refer it to show Language with It's flags as you want: 

https://www.simicart.com/blog/magento-2-multiple-stores-domains/

However, you need to note one important thing: when you create store, you need to fill the correct code of store that you made before, then the image will be displayed well. 

Look at it: