I have purposely saved the backspace (PC) or delete (Macintosh) key until the end, because I wanted you to think until this point that it wasn't even there!
To learn efficiently, it is best to always go slow enough that you can type with virtually no mistakes, so that you don't build up a memory full of wrong ways of doing things!
But now that you're nearing the end of the course, and will be back out in the real world of typing you will, unfortunately, from time to time change your mind about something you just typed, and/or make a few doosies!
The good news is, using the delete/backspace key is fun! The best way to think of it is like the fire button in a video game: when you have multiple things to delete don't hit it at the same rhythm as the rest of your typing, rather hit it rapid-fire style! As in, bam-bam-bam-bam-bam-bam-bam!! Pretend you're blowing up those mistakes! Which is, after all, what you're doing....
There are no exercises here for the delete/backspace key; you'll use it enough in real life!