I am confused at the use of open here.
The office opens early in the morning. The office starts early in the morning.
which is right? open or start?
The office opens early in the morning: it starts working at 9 o'clock.
One thing is about a condition (some place can be open or closed) the other is about an action (some work can start or end).
In English, we talk about businesses, and similar enterprises, “opening” each day rather than “beginning”. The reason for this is related to the idea that a business like a shop “opens” its doors to the public each morning, but the usage is the same for businesses that don’t interact with the public. So, for example:
The shop opens at 9am so I usually start work at about 8:30.
If we talk about an office or business “starting” or “commencing” we are usually referring to when it first commenced operation.