Fix grammar in step-by-step (#5958)

* Rewrote creating root node paragraph

I didn't like the sentence starting "It is equivalent" when it wasn't entirely clear what "It" was, so I edited. I'm not sure it's a great improvement!

* Changed reference to "disk" to "file"

* Fix grammar

"The example" sounds like it's referring to an example that has already been introduced

* Fix "like so" grammar

"Like so" is not used very often

* Remove "exactly"

"see how it works exactly" sounds odd, "see exactly how it works" is better, but to be honest it sounds best without "exactly" at all!

* Add missing "the"

getting_started/step_by_step/instancing.rst

@@ -8,12 +8,12 @@ a tree structure, with a single node as its root. You can split your project
 into any number of scenes. This feature helps you break down and organize your
 game's different components.
 
-You can create as many scenes as you'd like and save them to the disk with the
+You can create as many scenes as you'd like and save them as files with the
 ``.tscn`` extension, which stands for "text scene". The ``Label.tscn`` file from
 the previous lesson was an example. We call those files "Packed Scenes" as they
 pack information about your scene's content.
 
-Here's the example of a ball. It's composed of a :ref:`RigidBody2D
+Here's an example of a ball. It's composed of a :ref:`RigidBody2D
 <class_RigidBody2D>` node as its root named Ball, which allows the ball to fall
 and bounce on walls, a :ref:`Sprite <class_Sprite>` node, and a
 :ref:`CollisionShape2D <class_CollisionShape2D>`.
@@ -22,7 +22,7 @@ and bounce on walls, a :ref:`Sprite <class_Sprite>` node, and a
 
 Once you saved a scene, it works as a blueprint: you can reproduce it in other
 scenes as many times as you'd like. Replicating an object from a template like
-so is called **instancing**.
+this is called **instancing**.
 
 .. image:: img/instancing_ball_instances_example.png
 
@@ -38,7 +38,7 @@ scene.
 In practice
 -----------
 
-Let's use instancing in practice to see how it works exactly in Godot. We invite
+Let's use instancing in practice to see how it works in Godot. We invite
 you to download the ball's sample project we prepared for you:
 :download:`instancing.zip <files/instancing.zip>`.
 
@@ -107,7 +107,7 @@ There is more to instances. With this feature, you can:
 
 1. Change the properties of one ball without affecting the others using the
    Inspector.
-2. Change the default properties of every Ball by opening ``Ball.tscn`` scene
+2. Change the default properties of every Ball by opening the ``Ball.tscn`` scene
    and making a change to the Ball node there. Upon saving, all instances of the
    Ball in the project will see their values update.
 

getting_started/step_by_step/nodes_and_scenes.rst

@@ -72,16 +72,16 @@ editor.
 
 In an empty scene, the Scene dock on the left shows several options to add a
 root node quickly. "2D Scene" adds a Node2D node, "3D Scene" adds a Spatial
-node, "User Interface" adds a Control node, and "Other Node" lets you select any
-node. It is equivalent to pressing the "Add Child Node" button. These presets
-are here for convenience; they are not mandatory.
+node, and "User Interface" adds a Control node. These presets
+are here for convenience; they are not mandatory. "Other Node" lets you select any
+node to be the root node. In an empty scene, "Other Node" is equivalent to pressing
+the "Add Child Node" button at the top-left of the Scene dock, which usually adds
+a new node as a child of the currently selected node.
 
 We're going to add a single Label node to our scene. Its function is to draw
 text on the screen.
 
-Press the "Add Child Node" button at the top left of the Scene dock to create a
-node. This button adds the chosen node as a child of the currently selected one
-or, in an empty scene, as the root.
+Press the "Add Child Node" button or "Other Node" to create a root node.
 
 .. image:: img/nodes_and_scenes_02_scene_dock.png