What is the function of
'dass" in this sentence , could someone please explain?
In German, "to want sb. to do sth." is formed like "to want that sb. does sth." (subordinate clause): "The broadcaster wants that you work more."
Some more info on dass-clauses on easy-deutsch.de
What is the meaning of this sentence?
It is just a nonsensical Duo sentence that just means what it says. I cannot really explain it much more. It means that the broadcaster either wants him to work harder or work longer hours.
Can Sender mean, well, sender, as someone who sent the message?