There is a bug in ˝To be˝ lesson!
Please fix the bug in ˝To be˝ lesson, it's not possible to strenghten it, every time I finish timed practice it keeps returning me to the home page without any new xp or scale improvement. If anyone else has same problems please vote this thread up so the mods can see this.
This happened to me a few moments ago with some Czech lessons. I think it's a site problem that is not specific to Spanish, but it seems to have resolved for me after showing a "500 error".
Also, try to see if you can keep track of your XP if you are doing more lessons, it may have given some to you without notifying you.