A primeira alteração no manifest da esse erro abaixo
the element must be a direct child of the element
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.agenda">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".mainActivity"/>
</manifest>
