...e  I need some help that why I can't Rock smash the breezy crystal. 

Hi there @1660931851

 

The pokemon that has rock smash in your party necessitates an happiness level of 151+ in order to use rock smash on those crystals. It's good to denote that having a pickaxe will let you use rock smash without needing any pokemon that has the move. Those are obtainable through the coin shop or by trading with other players. 

 

You can see the current happiness of your pokemon by typing out the command ^happy 1 (The number refers to the slot of your party). Here's a few tips on how to obtain happiness quickly : 

 

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• You may obtain a free soothe bell from the NPC Tiggus in Celadon Office third floor. Putting this item on a pokemon will double his happiness gain. 
• Defeating and leveling up are the best way of getting happiness quickly, be careful to not let your pokemon faint or trade it as he will lose happiness then.  
• EV-reducing berries/Vitamins also gives happiness, but those are not affected by the aforementioned bell. 

 

You can read more in details on the topic in this thread if you are interested. Let me know if you have any other question/need clarification 

Have a splendid day!