Chrome and firefox Task manager

 >Click on settings

> Click on More tools

>Click on task manager

Firefox Zoom option for websites

 > Open Firefox

> Click on settings

>Click on zoom and click on default zoom to 110% or 125%

and there are other options such as font change etc.

Firefox dark mode or dark mode for all websites

 >Open firefox

> Click on settings

>Click on Firefox settings and Click on Dark mode

 

or You can go to themes and change the theme

or you can use extensions below:-

https://addons.mozilla.org/en-US/firefox/addon/darkreader/

https://addons.mozilla.org/en-US/firefox/addon/night-eye-dark-mode/