Can I read at least 3
DHT11 sensors using
GPIO with a Raspberry Pi 3?
And if yes, how?
Now I only have 1 DHT11 connected to the Raspberry Pi, but I used a library and I don't know how to add more sensors...
More detail would enable a better and more specific answer, but in generalities:
The library will almost certainly have some means of specifying the pin used by the module. For example using the Adafruit DHT-11/22 library you would make a call like this to construct a DHT-11 object:
dht = adafruit_dht.DHT22(board.D2)
board.D2 tells the library where the board is connected. To add an additional module you'd call the constructor again.
Take some time to read through the documentation for the module and your library. Then if you still need help tell us what you've tried and post the code that you're working on (or a relevant snippet).