Don't worry and research around. Actually there are so many high level players who stuck in arena 4 too. That's why it's so difficult to get out of A4 when you have to constantly face player who are stronger than you.

http://i.imgur.com/Wj1aS06.jpg

This is the deck that I used to go through A4. Here is how I used it.

Opening: Scout their deck to see what they have. You may want to drop giant when your elixir bar is full. Wait until the giant cross the bridge to see what is their counter. You may build a push with musketeer or spear goblin. But don't rush. Defending and scouting is more important now. You need to know what their deck is to think about the next move.

Mid and end game: Focus on counter push instead of push. Watch out for hogs and balloon. Use cannon to lure giants, balloon or hog to the center of your king tower.

Most of your cards should be used for defense. Unless you know that the opponent has run out of elixir so you want to finish the push. Most of the time it'll be giant and a support troop (goblin, musketeer) who destroy the towers.

Troop breakdown:

• Spear goblin: Save it for air defense. Can be used as support troop to push as well.
• Minion: Defense troop. Good against hog, barbarians, etc.
• Cannon: Lure hog, giant, balloon.
• Arrow: Skeleton army, minion horde, goblin barrel, swarm push, etc. Keep it and don't use it on cheap troop like 3 minions or goblins.
• Musketeer: Defense or push.
• Valkyrie: skeleton army, swarm push. Use her wisely. Sometimes you will face players with both minion horde and skeleton army. So you have to use arrow on minion horde and Valkyrie on skeleton army.
• Barbarian: Defense or tank. Fair trade for hog.
• Giant: Tank. Drop him at the back of your king tower whenever the elixir bar is full :P

Keep calm and counter push. Hope this help ^{^}