What should I do now
Unfortunately there's not much we can do either... =(
Skullgirls is a pretty demanding game, and the high quality art and backgrounds are taxing on most graphics cards built into phones.
We've tested performance bench marks with a Xiaomi Mi 5, which uses the Adreno 530 graphics card, and that produced great results (solid 25 - 30 FPS). Your device is using the Adreno 506, which is quite a bit older.
Here's a benchmark (scroll down) comparing performance of of the Adreno 530 vs the Adreno 506:
https://www.notebookcheck.net/Adreno-530-vs-Adreno-506_7062_7443.247598.0.html
Seems like your card is much worse than the one we tested previously (Xiaomi Mi 5) which didn't quite hit a perfect 30 FPS all the time, so this adds up to me. When we put an app on the Google Play Store, we know that not every device is going to have the hardware required to run the game, but the option is either:
A) Prevent those users from playing the game entirely. (Likely not your preferred option!)
B) Allow those users to play the game if they desire, even though the performance may be less than desirable.
We went with option B for most cases.
For more Android device compatibility details, you can check this thread here:
http://forum.skullgirlsmobile.com/threads/official-device-compatibility.113/
We're always making performance optimizations with each update, and hopefully we can get you closer to the performance benchmark you're looking for with each patch. Just keep in mind there is only so much optimization we can do, and it's likely you will need to upgrade your device to play Skullgirls smoothly.