Fullnode/websocket node

I want to run a testnet node where I can subscribe for the websocket. I tried to run the fullnode, so I start it as described on the page “how to run a fullnode” that wasn’t working. So I tried to download a snapshot. But I don’t know what to do with it, when I just use it as live, I will get an error of missing manifest (the manifest is referenced in the CURRENT file of the snapshot).
Is there a way to run the fullnode, or something simpler to be able to connect to websocket? (The official websockets are usually full, so I’m getting disconnected or I can’t connect at all)

Not yet, I’m downloading the new snapshot. I deleted the snapshot and I’m downloading a new one. But the new one looks like 1TB of data and the downloader doesn’t support resume.