Issues with timed practice
In general, I like the idea of timed practice, but there are problems with the current implementation.
Specifically, the different kinds of question formats take widely different times to complete. The three-alternative multiple-choice questions can often be answered in a couple of seconds, but some of the trickier and longer translations can take me more than a minute, as can some transcription exercises.
I hope at some point you are able to introduce some sort of weighting system--perhaps based on your records of how long users have spent on similar questions in the past. In the mean time, timed practise is very hit and miss and always over rather too quickly.
One other related annoyance: because timed practices always finish quickly for me, my default use of them is to do several practice sessions at a time. Currently, when I reach the end of any session where I have picked up at least one point, the default action is not "Practice again", but "Continue" to the Home screen. This is the wrong default action for me and I suspect it will be for most other users, too.