Note: I'm new to smartphones. Just tested the app for a few minutes. My phone:

-Bugs Found:
~When the typing screen appears, you should be able to make it hide by clicking outside when you're on the title screen. (I opened the typing screen in the deck building menu, then pushed a button on the top I think that made me go back to the title screen, and the typing screen was hiding all of my options on the title screen, forcing me to exit the game.)
~Game crashed in mid duel vs AI (I used Level Eater's effect (I used it before a lot of times in the duel) and the game exited, no messages, nothing, just poof!)

~How do you cancel a Chain? (I had a Quasar on field, activated the effect of TG Warwolf in hand, by accident hit yes if I wanted to chain with Quasar effect, and it did not let me cancel chain by pressing back)
"Use multitouch to cancel" how is that?
~Are deck files and replay files compatible with the android version? (from PC to Android)

Here a list of suggestions:

~Deck building menu:
Clicking some of the options on the deck construction menu it's close to impossible, the buttons are way too small (my res is 854x480).
On the search menu (to the right), you should be able to scroll through the cards by swipping your finger over them, (or maybe on the right part where the text and the scroll bar is) (swipping from down to up to go down, and viceversa).

~ VS AI Duel
Having to use both fingers to swipe down the windows is weird (Had level eater in grave, clicked grave and the menu appeared, took me a while to guess how to remove it, maybe some indication would be necessary, or just use 1 finger)  , implement sound, and for the most important part, make some feature or something to make the buttons bigger, this will become a great app.

Congratulations for your work, keep it on.