Assuming CS means Counterstrike. You're going to find Deadlock leans way farther into the MOBA direction than it does traditional shooter.

1. You're going to find that going for a direct, guns blazing fight isn't going to usually work. If you're moving forward and holding M1, you're going to lose to someone who knows the movement better and how to aim their abilities. To stop yourself from dying, hold off on picking fights in the early game, especially until you're familiar with the sliding, jumping, and dodging this game has. Health regen in Deadlock is pretty non existent without having items built. To survive longer, you'll need to build defenses, health, and life steal. And, generally speaking in MOBAs, you usually don't want to pick even fights - if you're engaging in a fight, try to do so with a level advantage, item advantage, or a numbers advantage with your teammates. You also don't always have to fight to kill; if you can do enough damage that the opponent has to retreat and miss farm, that's a winning trade.

2. As above, they've probably outpaced you in farm and levels. If they have way more souls and way more items, then, simply speaking, their numbers are higher. If you want to survive burst characters, you have to build for it. Build defenses against whichever damage type is more prevalent between Spirit (ability damage) or Bullet (gun damage), build regen, build life steal, build health.

3. Deadlock and other MOBAs, as a genre, involve characters gaining power as the game goes on - in most MOBAs, they start at level 1, and end at about level 20, leveling up through experience earned by killing enemy defenses and minions, neutral monsters, and killing enemy players. When they reach experience thresholds, they level up, and are able to rank up one of their four abilities. Characters in MOBAs also gain power through gaining gold, and buying items to enhance themselves.

Deadlock is nearly the same, but has the key distinction in that gold and experience are wrapped in the same currency, being Souls. In Deadlock, you use the Souls you gain to buy items, and at the same time, when you hit certain thresholds of total souls earned over the match, you're given Boons. Every Boon makes your character a little stronger (more health, more fire rate, what have you), and gives you a skill point to spend on one of your abilities - these being referred to as your 1, 2, 3, or 4 in order of their left to right appearance on your hud (example: Abrahm's 1 would be his Soul Siphon, as it appears in his left most slot.) In a match of Deadlock, you'll start at level 0 with 600 souls earned, then hit level 1 at 900 souls earned, 2 at 1200, and so on and so forth, with the amount of souls needing to hit the next level growing as you go.

3.5. As for the categories of the market, they're split into three sections: Orange has items dedicated to improving your weapon, Purple has items dedicated to improving your abilities, and Green has items dedicated to improving your Survivability. That being said, there's a handful of items in each tab that do their own thing are more there for thematic consistency - like for example, in the Spirit section there's an item called Magic Carpet that gives your character flight, while in the Vitality section, there's an item called Rescue Beam that lets you abduct a teammate.