how to change size of navigation view menu items and text?? How to change space between menu?

You can apply following Theme in your styles.xml for Navigation Drawer

<style name="NavigationTheme" parent="AppTheme">
    <item name="android:textSize">14sp</item>
    <item  name="android:textStyle">bold</item>
</style>

Apply this theme in Navigation Drawer

android:theme="@style/NavigationTheme"

Create following Theme in your styles.xml for Navigation Drawer and you're done.

<style name="NavigationTheme" parent="AppTheme">
    <item name="android:textSize">16sp</item>
    <item name="android:layout_marginBottom">02dp</item>
</style>

Apply this theme to your navigation drawer layout