Of where are you the child?
I am the child of here.
I am the manager of here.
Are these sentence having any grammatical mistake?
'Of here sounds a bit laboured in those contexts; many would say they're wrong.
Here are more natural-sounding alternatives:
- Where were you born/Where are you from?
- I'm from here/I'm a native <place-name>er (e.g. 'Londoner')/I was born here
- I'm the manager [around] here/I am the manager of this <whatever>.
b