A better practice
I would wish for a kind of "infinite practice" option, which pulls from all of your weak skills in random order, and just keeps on going as long as you like, or until the tree is golden.
Or if it could arrange the challenges to train the weakest skills (not the topmost weak skills in the tree as strengthening currently does!), that would be even smarter.
Anyway, i don't get why i should need to go through the "press strengthen, select timed or untimed, practice, acknowledge results" procedure multiple times if i want to train for 10-15 minutes in a row.
And i only get the last, most difficult skills presented if i guilded everything else before...
If it's about monetization (showing ads after each session) - make interstitial ads every 20 questions or so. A welcome pause.
I really like the idea. This form of practicing would better reflect real-life situations. I mean, you don't talk with people having in mind "adverbs", and then with other people having in mind "present tense".
In normal language usage, you have to use all the abilities you have acquired at once. Excellent idea, really.
I do not like the current system because your skills degrade so fast that I never actually get a chance to practice my more advanced lessons that I've taken. I wish they would at least randomize it or give you an option to rather than doing the most basic one or two skills in your practice.
the best practice is with doughnuts