How can i check if it downloaded the blockchain?
Pushpoold doesn't have anything to do with the blockchain. That's Bitcoin.
The blockchain is downloaded, normally, into the .bitcoin directory (under Linux).
You can perform a JSON-RPC call against your Bitcoin server to ask it what the latest block it knows about is...
I didn't say anything that implied that it did. I was simply stating that it will refuse to give out work because bitcoind won't give out any working information.