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.

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