interesting question --- in this complex sentence ONCE is a conjunction that may also mean as soon as. Now, try to replace it: The problem was solved AS SOON AS the manager arrived.

Hello Yagmur, this is a very common expression. "Once" here means as much as "when". It is used when an action needs to be completed before the main action can take place. Further examples: 1. Once I am done with this, I can help you with your homework. 2. We will leave for London, once the children have come home from school. I hope that helps :)

Once here means that at the moment the manager arrived, the problem was solved. There was no time lost.

Once refers here ' one time'