fill someone’s shoes
US /fɪl ˈsʌm.wʌnz ʃuːz/
UK /fɪl ˈsʌm.wʌnz ʃuːz/

1.
to take someone's place and do their job or duties as well as they did, especially when that person was very good at their job
:
•
It will be hard to fill his shoes after he retires; he was an exceptional leader.
•
No one can truly fill her shoes as the head of the department.