How to check if a user that i have the bearer is subscribed to a channel in helix?

I need to check if a user that used the oauth if he are subscribed.
Like that option in the legacy api is there anything like that without refreshing the token of the broadcast?

To check if a user is subscribed to a channel, you can use the Get Broadcaster Subscriptions endpoint

You will need a valid token from the broadcaster for that as it’s private information, and if you need to check users subscription status frequently then rather than individually checking it may be worthwhile to create a cache of subscribers, and the use Webhooks to update the cache to changes (you’d still need a broadcasters OAuth token with appropriate scopes, and it needs to be valid when creating/renewing the Webhook subscription).

Is there anything to use the token broadcaster without renewing it all the time like a authorization or something?

use the refresh token to get a new access token.

Refresh tokens do not have an expiry