How to make a perfect curve on the top header using (React Native)

Question

I start practice doing design in mobile application, I saw in google that I want to achieve in my mobile app, yes I did but the curve not perfectly same to that design. Here is the image from google.

This is my output that i already made in my application

I have here my codes,

Css:

    oval: {
    height: 100,
    borderBottomLeftRadius: 50,
    borderBottomRightRadius: 50,
  },

Html:

 <LinearGradient colors={['#00e4d0', '#5983e8']} style={{borderBottomLeftRadius: 100,borderBottomRightRadius: 100}}>
            <View style={styles.oval} />
        </LinearGradient>