@teastain Thanks, this is indeed basically the same as Felmue (Felix) has and it works also.
I compared the readings with the readings from a CO2-sensor. Temperature is close to each other (difference of about max. 0.2 Celsius). But the humidity differs about 8-9%. That is a lot. The sensors are adjacent to each wonder and should not differ so much regarding humidity (compared to a mechanic sensor, the CO2 sensor comes closest (difference of about 2-3%)).
I wonder how reliable the readings really are.
Thanks for the support anyway!