自分が大人になるまでの時間は長く感じましたが、子供の成長は早く感じます。
同じ20年間でも体感時間が異なるだろうことを言いたいです。（娘はまだ子供）
Comparing to the time until I grew up to an adult, It is gonna feel more quickly for my daughter to get an adult.でしょうか？
It feels like my daughter will become an adult much faster than the time it took me to reach adulthood.
この場合、次のような言い方ができますよ。
ーIt feels like my daughter will become an adult much faster than the time it took me to reach adulthood.
「私が成人するまでにかかった時間より、娘が大人になる方がかなり早い感じがする」
to become an adult で「大人になる・成人する」
to reach adulthood で「成人に達する」
ご参考まで！
It feels like my daughter will become an adult faster than I did.
"自分が成人するまでより娘がするまでの方が短く感じる"
- It feels like my daughter will become an adult faster than I did.
Comparing to the time until I grew up to an adult, It is gonna feel more quickly for my daughter to get an adult.
-> Compared to the time it took for me to become an adult, it feels like my daughter will take much less time to become one.
カナダ 
アメリカ合衆国 
