english verb tense app feedback

Hi, I'm a private english teacher living in Rio de Janeiro, and I made an app which I use with students to practice English phrase structures. I would like to ask other English teachers living in non-english countries to try the Teachers Mode - Practice-Verbal and give me some feedback on how useful it is to you (or not). So any feedback at all will be appreciated.
T.i.a.
Patrick

link on google play store https://play.google.com/store/apps/details?id=air.com.patrickjansen.net.TENSEDRILLER

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