Are foreign keys important while restoring database
If by "index" you truly mean index, then probably yes because the indexes are likely used to speed up read queries as well as lookups for when enforcing the FK constraint.

Of course this may not be true for all the indexes you currently have on FK columns, but that will depend very much upon your application. I would keep them all unless you have tested to make sure some are not needed (in which case those indexes could be dropped to save space).

As for the FK properties themselves, I would leave them in place. Rather than just limiting what gets inserted/updated to maintain referential integrity FKs also act as internal documentation for your DB.