Probably it's not even possible to run my project on a nano 
I got the message: Global variables use 2097 bytes (102%) of dynamic memory, leaving -49 bytes for local variables. Maximum is 2048 bytes.
but even after removing the temperature sensor and all it's code, it is still at 101%.
And I think to start with arduino, it is the least I can start with, one sensor and one display?
So either there is something wrong with my code, or I'm not sure what I'm doing wrong...
I plan to power it with micro usb