I have been answering emails since two hours today.
Is there anything wrong with this sentence? Yes, there is…
If you changed since to for, you’re right! Since is used when we talk about a point in time and for is used to talk about a duration or length of time.
Grammar point – for and since
For is used in the past, present or future to talk about a length of time.
He lived in New York for three years, but he no longer lives there. (past)
I have lived in Berlin for seven years already. (started in the past and continues to the present)
We will be in Italy for a couple of weeks. (future)
Since is used for a point in time in the past.
I’ve lived here since 2016.
Since I was a child, I’ve always loved running.