Good to know, though. As I went through all the lessons about a year ago, I don't really see it in context of a particular section of the course (I just use the "strengthen skills" button for my daily practices). It's a bit of a limitation that on the mobile platform I can't find the section notes for better explanation of these items.
Yes, some recent change in the Duo website has put it out of reach of mobile browsers for some reason. Apparently you can still get to the notes by using the 'Puffin' browser which you can download from the app stores.
You can also use a computer to get to the notes and then make a copy to keep handy.
There's an option in both iPhones and Android browsers that lets you see the desktop version of websites. Here's how to do it in iPhones' Safari browser http://www.idownloadblog.com/2015/09/16/how-to-request-desktop-site-safari-ios-9/
Am in this context means 'intend to' or 'intending to'. So the literally translation is 'I intend to get better in the Spring'.
Gwella could mean either improve from an illness or improve a skill or something else.
Therefore it's more likely to have the second meaning, although it could mean improving from an illness by the intention to look after oneself better.