I am pretty new to the whole app development stuff, and I'm just trying to learn the basics. Especially with XML I only have very little experience.
My problem is, that I want to add a button, which expands over the whole width of the screen, but it just won't work and leaves some kind of margin around it. I have already tried a lot, but I couldn't find any solution, or maybe I just didn't know what to exactly search for. One tip I found with the android:insets attributes didn't work, except for top and bottom insets.

[![enter image description here](https://i.stack.imgur.com/r8H7K.png)](https://i.stack.imgur.com/r8H7K.png)

This is my component tree:

[![enter image description here](https://i.stack.imgur.com/Vhiha.png)](https://i.stack.imgur.com/Vhiha.png)

And this is the XML:

```
<?xml version="1.0" encoding="utf-8"?>
    <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/bg_2"
        tools:context=".ApplicationActivity">

        <com.google.android.material.button.MaterialButton
            android:id="@+id/backBtn"
            android:layout_width="450dp"
            android:layout_height="59dp"
            android:background="@drawable/back_btn_bg"
            android:fontFamily="@font/montserrat_thin"
            android:insetLeft="0dp"
            android:insetTop="0dp"
            android:insetRight="0dp"
            android:insetBottom="0dp"
            android:text="@string/back_btn"
            app:backgroundTint="#470000"
            app:cornerRadius="0dp"
            app:fontFamily="@font/montserrat_thin"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent" />

    </androidx.constraintlayout.widget.ConstraintLayout>

```

I hope I included every information that's needed.
Thank you in advance :)