which / who is the taller of the two girls?
How many/ much fruit does your father produce everyday?
- Who is the taller of the two girls. (sounds very formal and like literary English from a novel)
- Which girl is taller? (something I would say)
- Which one of the girls is taller? (something I would say)
Both, I’d say, are acceptable.
As there are two definite persons, you may also use WHICH. (Which of the two girls is taller? - Here WHICH ONE is not necessary)
However, Who is the taller of the two girls? is more common.
Your second question, ‘How many/ much fruit does your father produce everyday?’ has two errors.
- FRUIT being a non-count noun here, ‘** How much fruit**’ would be better.
(How many fruits or types of fruits’ is also possible)
- The use of everyday is not correct. It should be every day.