As you are using Formik here you dont have to maintain a component level state for email here.

You can do like below which will use the state of Formik and can get that when using the handleSubmit, Sample code would be like below.

<Formik
  initialValues={{
    Email: 'test1@gmail.com',
  }}
  onSubmit={(values) => {
    console.log('submit');
    alert(values.Email);
  }}>
  {({
    handleChange,
    handleBlur,
    handleSubmit,
    values,
    errors,
    isValid,
    touched,
    setFieldValue,
  }) => (
    <View style={formStyles.SectionStyle}>
      <TextInput
        name="Email"
        value={values['Email']}
        style={formStyles.inputStyle}
        underlineColorAndroid="#f000"
        placeholderTextColor="#8b9cb5"
        keyboardType="email-address"
        onChangeText={handleChange('Email')}
      />
      <Button title="Submit" onPress={handleSubmit}/>
    </View>
  )}
</Formik>

Instead of the hardcoded value for initial value, you can use your email address that you retrieve from your database (or API)