Return to Sender
After jumping off the truck, kill all enemies outside until you get the chance to use the remote chopper gun. Use it to whittle down enemy forces. Continue fighting your way towards the mansion. Enter the building to the left side, in front of the mansion then go to the third floor. Kill all enemies inside then grab the intel.
This is the best time to attempt to achievement “Killbox”. You'll have to kill 20 enemies using the remote mini-gun. See the video below.
Like picking off ants who fire back
After clearing the MG nests, continue inside the mansion and continue to the second floor. Kill the remaining stragglers then breach the door in Waraabe's office. Kill all guards except him then grab the second intel on the table behind him.
Head to the LZ and take cover as soon as the ambush sets it. You'll have to make it to the second LZ before the time runs out. Kill all enemy forces along the way as fast as you can. Once you've reached the point where the enemy pushes a burning car towards you, take note of the small building to the right called the Money Market. That's where the last intel in this mission is located.
Money Market Intel
Head to the unfinished building and fight your way to the top floor. Once you reached the top floor, use the remote gun to thin out the enemy forces. Nikolai will still get hit. Immediately run towards the rope and use it to go down.
Follow Price and take out the enemies as needed. Continue moving forth until you reach Nikolai. After reaching him, carry him and make your way to Echo Team's location.