How to get block data from celestia node

how to get data from data availability layer of celestia with RPC ?

Hey there! You can use the header method:
https://node-rpc-docs.celestia.org/#header

For more information on how to use the available APIs, please see:
https://docs.celestia.org/category/rpc-api/
https://docs.celestia.org/developers/node-gateway-docs/