today I updated the game but there is no Arid Ruins.
You posted this in Android Chat. Android update was not today, and it has no Arid Ruins issues.
Amazon and WP have issues with Arid Ruins and you should find relevant details once you check the forum appropriate to your platform (probably WP).
Name: Rusty (Rustyx in game)
Guild title: resident wisenheimer.
Line ID: Rustytroll (big shock there, eh?)
If you are talking about WP than Arid Ruins isn't opened yet, but it will be on Wednesday after most if not all of players will have most recent version.
You can read it here: [News] Castle Clash Update on Mar 19 (WP/WS) [Version 1.4.5]
So we kindly ask for patience to wait for few more days.
If this is different platform, than write. On Android it should work without any problem (if not counting bugs)