What are the main languages spoken by Hindus?

Most of the sacred books of Hinduism are written in Sanskrit and the script is called Devanagiri. However, Sanskrit is no longer in common use.

No particular language is main for all the Hindus. A majority of Indians are Hindus. but that doesn't mean that we speak the same language. Not all Hindus speak Hindi. Similarly, not all Hindi speaking people are Hindus.