@mfalkvidd Yes, a DH11. Regarding the code running on the NodeMcu, could you please send me a link to an example explaining how to receive the data transmitted by the Arduino Nano? It would help me a lot if I could see an example showing what the methods "setup" , "presentation" and "loop" should contain.

@mfalkvidd I actually use a different kind of temperature/humidity sensor. I will adjust the Arduino sketch and try. Thanks a lot.

That would work for a local temperature sensor connected directly to the NodeMcu.
What I would like to achieve is different. I would like to use a NodeMcu as gateway.
It should be able to receive data from different sensors in my house.
For the radio communication I´d like to use an inexpensive NRF24 transceiver.

@mfalkvidd I´m just looking for an easy way of receiving temperature data transmitted by 3 Arduino Nano connected to a NRF24.
I´d like to use a NodeMCU connected to a NRF24 to receive the temperature data from the 3 Arduino Nano and make them available over WifI to my cell phone. Can I use the mysensor library to receive data transmitted using a different library (https://github.com/TMRh20/RF24/blob/master/RF24.h)? Can it work in principle? Or should the transmitter use the mysensor library too?

I connected my NodeMCU to a nRF24L01 as explained at
https://www.mysensors.org/build/esp8266_gateway

I don´t know how to listen to messages from a pipe.

The corresponding NR24 API for Arduino supports the function openReadingPipe:
https://www.mysensors.org/build/esp8266_gateway

https://github.com/mysensors/MySensors/blob/development/drivers/RF24/RF24.h

I have a question regarding the API to access the sensor nRF24L01.
What happened to the function RF24_openReadingPipe?
It used to be part of the API.
Has it removed because it is obsolete.
What it is the right way to read data from a pipe?