Seeking help with Legends of Runeterra [Beginner]

Hello there, I am new to the game and I got some questions

hoping someone would help me with them :) 

1 : what is the QuickAttack ? I read what it says, but I can't seem to see any difference from normal cards ?

2 : What is a discard ?

3 : How to counter Tryndamere ? I might be wrong but, isn't the idea of leveling up when you die a bit too powerful ? How do I win against him ?

Thanks.

Heya, hope you enjoy the game.

1: Quick Attack means that when that unit attacks, it strikes first (before the blocking unit). If its damange is sufficient to kill the blocker, the fight will be over without the enemy unit being able to inflict any damage in retaliation.

2: To discard means to remove/eliminate a card from your hand.

3: True, under most circumstances, you cannot prevent Tryndamere from leveling up. However, his mana cost is quite high to compensate. Your best bet is to either end the game before Tryndamere can hit the field (or before he can make a meaningful difference) or to use effects such as stuns, recalls, or outright kill effects to slow him down or remove him. If he stays on the field for a couple of turns, there's a good chance he will decide the outcome of the game, but the same is true for other high-cost units (including champions such as Anivia).

Quote From AbdullahHejazi

1 : what is the QuickAttack ? I read what it says, but I can't seem to see any difference from normal cards ?

 

Did you play through all the tutorial missions?  I know they can be a little dull, but they do cover things like this and they also give you a respectable amount of bonus XP.

Pretty much what BlueSpark said, + frost effects.

Just to be fair, Tryndamere is the second hardest unit in this game to remove from the field, just behind Ledros.
Now, if you really need to get rid of him for good, just like in the moba game, you will have to kill him twice.
Notice that his first form has 8/4 stats. The best way to do it, is to deal 4 damage to him (usually done defending with a follower with 4+ attack) and then play a killing spell like vengeance after he levels up.

Also, something that even some veteran players fail to realize is that Tryndamere only levels up once per game.
If someone have 3 copies of Tryndamere in their deck, it will be needed to kill him twice only the first time. The remaining 2 copies will be already leveled up as 9/9 Fearsome + Overwhelm. Thats still good but not amazing stats for a Champion with an 8 mana cost.

Got it, thank you for the help <3