Person = { 'name' : " Jehn", ' age':23}
Sentence= f' My name is {person ['name']} and i am {person['age']} years old.'
You can change the type of quoting in the format string so it is wrapped with double-quotes like this:
person = { 'name' : " Jehn", 'age':23}
sentence = f" My name is {person ['name']} and i am {person['age']} years old."
Note that there was also space in ' age'
which could be missed easily. Also, I changed the variables to be all lowercase letters to be more Pythonic and consistent.