How to increase my android application performance ?

If you want to have high-quality graphics you need to consider that not all mobile devices are same. Some are old and behind the level of latest technologies. What you can do is lower the quality of the textures. Try making tests on your game. Check what scenes or objects puts the most pressure on your device. Debug it one by one. Besides than that, unity has some built-in mechanics for optimization such as occlusion culling. Check them out. Try to use low poly objects. Use lower quality textures. Also depending on your game, you can try to increase Fixed Timestep. There are many small tweaks like these. That's what I can suggest to you. I had the same issue 2 years ago. I forgot that I was making a game for mobile devices and created a graphically and physically beautiful game. When I started testing it on my mobile phone game wasn't even running. It was getting stuck at loading scene, even it does load it was lagging as hell. I spent a week on just optimizing the game before releasing it. It is part of the process and it is the best process. When you get to optimization it means that your game is really close to release.

So good luck my friend and I wish you the best ^^