Shoot at the enemy machine gun

positions at the stairway or behind the cover next to them and kill as many as you can
The first one is easier to solve the second one is farther away and there are enemies not only in one direction and it's dark so you need to be careful. The second machine gun position is also blown up after killing the larger threat of enemies in the target apartment building then find cover while rushing up kill downstairs and wait for your teammates to throw a grenade into the house to blow up the enemies and then go in. It doesn't matter if you use a shotgun in the house it's just that you think it's more atmospheric. After killing all the enemies go outside and meet up with your friends and get into the Humvee to go to the next battle site.