This site is great but don't expect to become fluent using using this one only. It's a bit like Duolingo. It can give you a kickstart but real morse on air is different.
Real Morse is only different when you start after finishing lesson 40 with 20/10 using that on the bands, and requesting for QRS. It turns out you even can't copy machine generated keyboard code 12/12.
You better learn after lesson 40 correctly spaced Morse code first. That is fastest with the same throughput (characters per minute) by adapting from 20/10 to 13/13 and from 20/5 to 9/9.