How can I construct this sentence "The manager of the representative"? I mean about something like this: "representative's manager"
The full sentence is:
The manager of the representative said to us "Now, We are going to new way".
To condense this phrase "The manager of the representative" to three words:
The representative's manager
So putting this into your example:
The representative's manager said to us "Now, we are going a new way".
The other changes:
1) "we" is not capitalized.
2) The usual way to say this is "going a new way", meaning going in a new (business) direction.
Possibly you could say "going to a new way", but way is a countable noun so an article is needed.