iPhone XS heating

My iPhone XS is very heating from the part under camera and down while using small applications like facebook on 4G witch is not a correct case I think

i am not talking about Heavy load like playing PUBG or else, I am talking just about browsing Facebook or YouTube throw their official application for a time with my 4G SIM card

i supposed that I buy the most powerful Phone not a Normal one

using Facebook around half hour or YouTube about half hour

and I am at cold area around 18 C so please don’t tell me you are in a hot place and don’t tell me you don’t need to watch Facebook for an hour or please use WiFi because all these are not logic completely

i don’t know why this happened so please advice