mysql query high problem

I don't quite understand what you mean, but it there is high load you can't really fix that. You can optimise tables which can speed up queries, but you'll need to add more servers in a round robin eventually. You can tweak with MySQL settings to achieve the best.
 
The most common problem is that your Mysql server is only optimized for MyISAM and not for Innodb tables (used by Xenforo). Ask your host to optimize this (e.g. activate caching for Innodb).
 
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