[Melissalala]

When I try to highlight something to erase that entire highlighted part, it
only goes to the beginning where I started the highlight.

Like if I try to highlight to erase that whole part..:

The dog is cool.

It will only bring the flashing | - thing to the beginning of that sentence.

[Daiya Mitchell]

Probably you need to check the box that says "typing replaces
selection." It might be in Tools | Options | Edit, or it might be
somewhere in Tools | AutoCorrect, depends on your version (which you
didn't specify). Backspace counts as typing, in Word's view.

Melissalala wrote:
When I try to highlight something to erase that entire highlighted part, it
only goes to the beginning where I started the highlight.

Like if I try to highlight to erase that whole part..:

The dog is cool.

It will only bring the flashing | - thing to the beginning of that sentence.