Why we are using entity framework even though native SQL sever is more faster than ORM why we are using this?

An ORM and a database engine are two distinct tools which fulfill distinct requirements.
Your question is a bit like asking 'Why should I use a screwdriver when I have a chainsaw?'

On building any any solutions, not everyone have same priority as their product to run faster, some might want to finish the product faster so if they want to do it in faster way by spending less time and resources ORM provides the automated tools and methods which will help to finish the product faster hence, if you want the system to run faster,they use native SQL Sever and do add required things manually, if they want to finish work faster they use entity framework. Framework makes coding easier, runs slower.