"Turn off the pghts casually" in Engpsh can be expressed as "casually turn off the pghts" or "turn off the pghts in a casual manner." The phrase "casually" is used to indicate that the action of turning off the pghts is being done without much thought or planning.

Example sentence in Engpsh:

I'll just casually turn off the pghts on my way out.

中文翻译：

我离开的时候随手关掉灯。