Extends a module from design folder
1- Create de folder app/design/frontend/Vendorname/themename/VendorName_Modulename/(all the files that you wanna extends from view/frontend/ of the module to extend)
Ej: If you wanna extend
app/code/TopGroup/ComparadorPrecios/view/frontend/web/css/comparadorpreciostp.css
You have to create
app/design/frontend/TopGroup/carrefour/TopGroup_ComparadorPrecios/web/css/comparadorpreciostp.css