its not only when you learn torah and daven that you'r serving hashem!
when you do or eat something "gashmiyus"
and you think "i'm eating this to have chayus to serve hashem!!" or "i'm doing this to be able to serve hashem better" then because you'r using or eating it to serve hashem better it's not gashmiyus anymore it's ruchniyus because it's being used or eaten to serve hashem better