I gave this a shot for a couple of minutes. Have some feedback, but it'd be great to know what your target audience is, and what kind of feedback you are specifically looking for.
It looks like you have a decent list of different game modes for a user to engage with. Also, the scoring and reward system at the end of completions is nice. The design is clunkier from what I would want from a brain-training app, though. This makes me unsure about your target audience. Is it for children? Is it for the elderly? These can make a significant difference in how it's best to present learning material.
Overall, I think there are some interesting things offered here mechanically speaking. The UI/UX and design around the material don't work for me. But there is a lot of potential here.