How to add elements to LinearLayout?

Question

XML

Hello, I have this code. You need to add 3 textview elements on top of the existing ones (a header for the table). How to do this, I have already twisted all the forums, everything floats and does not work. There is no time to study layout comprehensively.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="Horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:minWidth="25px"
    android:minHeight="25px"
    android:weightSum="100">
    <TextView
        android:text="Name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="25"
        android:id="@+id/txtId" />
    <TextView
        android:text="Last Name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="25"
        android:id="@+id/txtName " />
    <TextView
        android:text="Age"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="25"
        android:id="@+id/txtPrice " />
    <TextView
        android:text="Gender"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
             android:layout_weight ="25"
        android:id="@+id/txtQuantity" />
</LinearLayout>

Here is the result of the code