Do u want tips for the match or tips in that stage against MK?
Well, vs MK u need to camper because he can pillar ur shield very easy and in the air u get *****, but Brinstar doesn't allow u to camp him, u need to pay attention in every MK's mistakes. U have quick tilts dude, i really missed Dtilts and Ftitls OoS. Dsmash is aso a great option OoS. For kills, i think Usmash under the side plattforms is a nice option(obviously when MK is above one of them), Nair and Bair also kill early because the stage allow u to do so. So, predict ur oponet's Air Dodges. Talking more about ADs, avoid some, MK can get early Up B kills. Also, avoid some silly rolls, like A2Z said.
Beating MK's Up in the ground the only option i see is Power Shield because it has some invencibility startup frames. When PSed, Jump OsS and i see Uair as a good option. If u miss what i've said and MK come for a glide, try Bair, it has the some priority.
NEVER, never go off-stage against MK =X
In neutral stages as i said, camp is the best option, but one time u'll need to approach so as to kill. I see Full Glide Toos to Nair/Fsmash as a good option, but just approach when u feel confortable so as not to be hardly punished.