Make the sentences passive. we watch current news on television every evening. i think they have already forgotten those sad events. we will cater for kids of different ages. i knew the bad news had depressed everybody. when we returned home, our parents were discussing something excitedly. –may i help you sir? -no, thanks. they are already serving me.

We watch current news on television every evening.
Current news is watched on television by us every evening
I think they have already forgotten those sad events.
I think Those sad events have already been forgotten  by them
We will cater for kids of different ages.
Kids of different ages. will be catered for  by us 
I knew the bad news had depressed everybody.
I knew everybody  had been depressed because of bad news 
When we returned home, our parents were discussing something excitedly.
When we returned home something excitedly was being discussed by our parents 
–May I help you sir?-No, thanks. They are already serving me.
May I help you sir?-No, thanks. I am already being served by them