? is the start of the querystring, each parameter/value pair is separated with an &, not ?, which is why your first 2 didn’t work as intended.
Also, you’re still using kraken, the new API would be https://api.twitch.tv/helix/streams?first=20&community_id=4d2aef2c-35f5-40b3-8a0e-35a79d7175c5
this returns the first 20 streams with that community ID in a data array, there’s also a pagination field which contains a cursor which can be set as the after querystring parameter to fetch the next set of results (which will contain a cursor for the next page, and so on).