macbook pro 13 getting very hot when connecting to Monitor

Hi, everyone here! I would like to ask a question here, why my macbook pro 13(mid 2014) getting very hot when I connect it to Dell U2515H?

is it possible that there are some graphics problem? I also have another problem, I click the powder on button, I could hear the apple sound,

then black screen for 15-20 seconds before it lights with log in? do you guys have similar problem? Thank you very much!

Cheers,

Jiami