Thank you very much for your sleep code and the tips to reduce the power consumption.
It took me a bit longer to get it working, but it does work now.
I can`t even meassure the power consumption with my multimeter. It is below 0.1microA when sleeping.
To send the Code I need to send it around 35 times to receive it 4 times.
I connected the Button and external Pullup like in this picture:
