First of all, welcome to Zammad.
Secondly, just a wild guess, you’re not using the API with an API-Token, di you?
If you use basic authentication, please note that this has tons of downsides (apart from performance) and might even end up in time outs. If possible, always stick to API tokens.
Normal GET requests shouldn’t take too much time then.
If you have the information you’re showing on the TV within a overview anyway, you could also just poll the overview endpoint which currently contains Organization, User and Ticket-Information and should be working just fine.
Regarding querying overviews via API, the following Post might help you: