How do i complete the defend the warehouse favor?

yep.
I am now the don.
when i did it, it takes fire power.
find cover and shoot, my best suggestion is to stock up on guns and ammo at the house's and weapon dealers.

It took me being Don of NYC and having unlimited ammo

easiest way i found was to ensure you have a level 3 or 4 weapon prefrebally the annihalator.
and also to recruit a crew member

Once equipped after talking to the puppet turn facing the entrance of warehouse go into free aim and unload two shots from annihalator into the vans that drive in they soon blow up knocking the stracci to the ground

now run to the warehouse entrance on your left and then leg it down the stairs to the opposite side of the room under the walkway. should be a few crates. now you have no chance of been snuck up on and let them come to you.
about 3/4 of them will come after you but just pick them off when no more come then its time to carefuly head back to where you came in

a stracci should be guarding outside the door blast him, and then two or three more will be down the stairs in front of you be careful and you should be fine after these are gone head to where the cars came in and slowly make your way to the entrance picking off and remaining stracci and you should be done

I friking have all level friking 3 Weapons, Don, level 5 Assassin Crew member and I still cant MOTHER Fing PASS IT, I have one Barzini Store left to take over and it has 28 minutes to repair, I have two Executions left, everything else is done except for Hit Contracts and Favors(I'm close I think)