Unable to operate NEDIS (/tuya) SmartLife wall switch

Hello Sasja and welcome.

Return the Nedis wifi devices
I’d go for non-cloud dependent devices, like zigbee based devices;
Or,
if that’s not possible / you don’t want to,
Install the Tuya Cloud community app and use that one (it’s unmaintained though), instead of the ‘official’ app, which is on hold/frozen/left to die and hidden from the app store.
Also, Athom founders said about Tuya “I shouldn’t buy that stuff” (and worse). Meaning Homey & Tuya combination is going downhill.

https://community.homey.app/t/app-tuya-connect-any-tuya-device-with-homey-by-tuya-inc-athom/106779/963