Hey njonas45,
We understand you're trying to use your Apple TV remote to turn on/off your Optoma projector. We'd be happy to help out.
While we couldn't say definitively whether this is possible for your particular projector, if it is, you can find help with getting that set up using the steps outlined here: Control your TV and volume with the Siri Remote - Apple Support
If that doesn't work for you, we'd suggest contacting Optoma for more info on whether or not this is possible to configure or not since it's a question specific to their product.
Thanks for using Apple Support Communities.
Take care!