Dynam Smart Trainer Battery Recommendation

Maksym

Full Scale Pilot
I just got my first R/C plane recently(Dynam Smart Trainer), and it flies very nice and easy to control. I've been told that the plane wasn't a good choice, but for me it's easy to fly and that's good enough.
Anyway with flying aside I would like to ask what extra battery I should buy that will be safe for my plane. Currently I'm using a 25C, 2600mAh battery. The plane only flies for about 5 minutes and then runs out of charge. That's something that I would like to get fixed and would like to know what other battery I can buy for my plane.

-Maksym Medvid