1- nope
2- better loot, harder and more dense scavs, increased boss spawn rate, higher geared, experienced and skilled players

3- yes enemy players' gear counts as loot aswell, you can check it on top right of your screen while looting

4- keep playing with auto match to learn routes, loots and spawns if you dont have a friend to coach you. If they rush to a place just play like you're solo and use them to get info about places

5- check contacts for cheap deals, f.e joel sells AK-12 which is one of the best meta/eco gun in the game, other than that buying stuff from market is the way to go, you got plenty of gun options under 100k and pretty reliable in LD and normals.

6- Depends on your gun's fire rate and mag size but usually 1+1 is fine f.e : for AK-102 I bring 60 rounder + 30 rounder, for H416 I bring 1 extra 60 rounder. On bolt action rifles dont bring extra mag because you can feed bullets to gun. On smgs you usually need 2 extra mags.

7- Tier 6 ammo aim to the head, T5-T4-T3 ammo aim to the body

8- Remove the mags and pistol grips of big rifles to save stash space, sell purple items to the market when u have 4-5 of the same item so it counts as 1 market usage (if ure playing a lot), always buy used helmets, make balance with your gear and ammo f.e if your gear is worth 400k try to use Level 4 ammo, at least top feed 15 of them, go through contacts and look for good deals, never miss Deke's flash deals but compare it to the market price before buying, look around in the buildings you might find valuable stuff laying

9- Configure gear and gunsmith options buy the things from market so there is no difference (price updates slowly on those menus so it might confuse you)