FPS Android

Because my android game has fps slumps
and what would be a possible solution

The game goes well, but after playing a few times it drops 20 fps more than normal in the same scene.

 

Profiling it and seeing whats going on.

I assume you're accumulating garbage somehow if it gets worse and worse as time goes on

 

I think it's my cell phone, because in unity I play several times and the fps do not go down.

But I still do not understand because first things go well and then the fps go down..

 

Sometimes mobile devices will get some heavy network traffic and that will make all apps running lag out a bit, especially if there are apps like Facebook or Twitter or other apps listening to the inbound network traffic and making decisions about it.

Redo your testing again but this time put your phone into airplane mode, see if you still get weird lags. If you do, then as @SparrowsNest points out, it's time to attach the profiler and start trying to get a handle on where it is choking up.