Halo 5 is just not working for me

First I wanna start by saying,yes I have contacted Microsoft for support but they haven’t been able help and no,its not my internet because all other games I play run fine.So whenever I open up halo 5 it laggs,even when I play the campaign off line!it just won’t work and really starting to get annoying and could really use your help 343.Please help need!