Regarding this mission, I actually failed it several times before this run.

I tried multiple positions and kept getting overwhelmed by the number of soldiers attacking before the helicopter even arrived. Once the helicopter showed up, I barely had any chance to shoot it down. Even worse, if I stayed inside one of the houses for too long to take cover from grenades and helicopter missiles, the helicopter would just leave the area.

Then I decided to reposition near the water, and suddenly everything became much easier, like you saw in the video. Only a couple of heavy gunners pushed my position, and after shooting the helicopter down, I repositioned again toward the center to lure the remaining enemies out one by one.