Please explaine step by step how to get to sunyshore city Heres some things..

Now stock up on these items:
10-20 max potions, 5-10 revives, 5-10 full heals, 20-30 dusk balls, 5 max repels, and 1 escape rope. The amount of healing items depend on your ability as a trainer and the level of your pokemon. The amount of dusk balls depend on your ability to catch Pokemon [get it's HP in the red zone, status infliction, etc.] The max repels are plenty because I explored ALL OVER and I had 1 left, still. The escape rope is so that you can escape easily. [Fly doesn't work on Spear Pillar.]
Also have a team with a Pokemon in the high level 40's, and Pokemon that knows these HM's: HM03 Surf, HM04 Strength, HM06 Rock Smash, HM08 Rock Climb.
Now fly to Oreburgh City and go onto Route 207, and go up the slope. Go east and into Mt. Coronet. Surf across the water and go up the wall using Rock Climb. Go the the northern part of this room and go in the cave. Just follow the path until you are on the mountainside. Excluding the cave you just came from, there are 2 caves to enter. One will be a dead end, with some Galactic members to battle to train yourself up. The other will the continuation of Mt. Coronet. Once you find the correct cave, follow that until you are on the second mountainside. The same thing as the first; there are 2 caves, and one will be a dead end with a guy who is blocking a doorway saying he has no pokemon; pathetically, this has fooled many people in the past. Uh duh, YOU'RE IN THE WRONG ROOM. So get out and find the other one all the way to the west. Just follow that path and you'll eventually be on Spear Pillar.
In Spear Pillar, there will be multiple fights, including the legendary Pokemon of Diamond, Dialga. This is why I reccomended 20-30 Dusk Balls.
There will be 2 grunts you will have to fight. And then there's Mars and Jupiter. And after them, there's Cyrus. And once you're done with them, there's Dialga.
The 2 grunts aren't any trouble, so don't worry about them. You'll fight Mars and Jupiter with your rival, so you'll have backup this time. After the fight, he'll heal your team up, and now you go to fight Cyrus, who has leveled up quite a few levels in such a short time. They're all beaten with rock moves, so yeah... After this, heal up if necessary, and SAVE YOUR GAME. Continue when it is night.
Now go on and fight Dialga, get his HP to the red zone, and inflict a status problem if possible. Then just start throwing Dusk Balls! [Do NOT waste your Master Ball on Dialga.] And then you're done! And now you can go to Sunnyshore City.

First you have to go to mt. Coronet and you have to surf across thenwork your way to the top and then you'll fight a couple battles and catch dialga. Then you can get to sunyshore.

You have to Catch Dialga, then the guy moves.