I never played that much adc but last days I really got intrested and started learning matchups,champs and that kinda stuff. But I lose many of my games I have about 48% win raye in 25 last games. My farm isn't bad but I fall in late game. Also I sometimes do great but my autofill supp makes stupid plays. How to win with bad supp and how to win more games as adc in general,should I only spam the role until I acomplish good win rate?
play 
she is strong early and late game but she have only 1 mobility W jump 900 range
strong and good to survive against assassin with E and R
she is weak early game but when she get critical chance she carry the game hard
Okay, some quick tips:
Basics
Learn the mechanics ADC is the most mechanically intensive role in the game. You need to always be moving, and whenever possible, orbwalk. The Attack-Move-Click is your friend. By default, this is <SHIFT> + Right-click, but you want to rebind that to a dedicated mouse button. (Most prefer the left click.) From there, you should learn the concept of autospacing and apply that to kiting. Essentially, use your range to keep your opponent at bay. Whenever he/she advances, you pull back a bit and attack. NEVER go into melee range if you can avoid it. You have to be like Muhammad Ali: Stick and Move.
Know what to build
You aren't going to get very far if you don't know what you're building and which runes to take. For my money, runeforge.gg is the place to help you with your runepages, and eune.op.gg will help you with your builds. In general, Attack Damage and Crit should be your priorities, with attack speed and lifesteal being your secondaries. If you're dealing with a fed mage/assassin or are just behind in general, 
and 
are your best friends. Which leads me to point 3.
Avoid Mages/Assassins
(Unless you're super ahead.)
If they can burst down a squishy simply by rolling their faces on a keyboard, run. If they're ahead, run. If they're even with you, run. If they're only one level behind you, run. The only time you should be thinking about dueling them is if you're the most fed player in the game and have a good three levels and an item on these guys. Preferably while standing behind a tank or juggernaut. Speaking of those, THOSE are your rightful prey. Tanks are melee fighters who do little damage. With a tank busting item or two (
), your DPS will melt their HP at 750 per second.
Don't go it alone Try to make sure you're with the whole team or even a couple of members when you're on the rift/treeline/abyss. If you get caught out alone, generally speaking, you won't do very well. You need a front line to take the damage for you while you're doing your job of causing as much damage as possible to the pick/enemy combatants. Post-laning-phase, get with your teammates, help them with their lanes, and get picks that way.
And finally, the no-brainer...
Being next to the dragon, bot lane is prime real estate. Expect and be prepared for the jungler and mid-laner to gank sooner, rather than later. A well-placed ward will get you out sooner rather than later. If you're in a team fight, you'll be able to see an assassin try to flank around to get to you this way. When you're playing, it's like driving; the mini-map is the rear-view mirror. Every so often, take a look at it so you don't get hypnotized by the road. NEVER go past river unless the enemy jungle is warded.
Team-fighting
Know your position Your position is in the back-line, behind the tanks, bruisers, and juggernauts. If they fall back or die, you fall back. I don't care how low an enemy team member is, if you try to chase through the enemy team then you're going through a spanking machine and you might not even get the guy. Stand behind your bruisers, let them protect you while you do the job of dealing the damage and mopping up.
Don't initiate
Unless you have a utility carry like 
, leave the initiation to the support or the tank. They'll lock someone down for you; you blow them up.
Focus the enemy carry Whoever's been carrying the most on the enemy team, that's who you want dead. If you kill the carry, the other side just might fall apart, which makes your job that much easier. By that same token, if you've been carrying up to that point, expect the enemy team to try to focus you.
4)When in doubt, know your way out If you're going to lose the team fight, try to find an escape route to a safe recall place to get back to fountain. Or barring that, execute. Remember, the most important thing you can do for your team is to stay alive.
5)Make sure you can get something off of the team-fight Winning a team-fight is okay, but try to get an objective afterward. Otherwise, it wasn't worth it to have a team-fight in the first place. The point of a team-fight is to clear the way so that you can take objectives. Winning one late-game team-fight can win you the game if you know how to capitalize on it properly.
