Mobs are not spawning from spawners when i am away from it

Hello from india and love from india .
I am a pocket edition player i am reporting a bug first time plz
Fix it when i get spawners and when make a farm their i have to
Stay their for long to spawn mobs it is not working afk

And one more rabbit are not faster or fast when i go near them they
Have to ran fast as cats right but they are so slow and they are
Horse are not getting ride thnx👍 i hope you will gix it