Hello

I wanna ask regarding battery voltages. I have it showing on my main screen.
So sometimes it turns yellow and you should not push sticks too hard those moments.
But what about after they go back to green?

And also i wanna ask, is it ok if voltage turns yellow when RTH?

Depending on what firmware you have, the app should warn you if you are pushing the motors too hard, and it will reduce the power to the motors in that case.  If it turns yellow it is a clear indication the battery is nearing exhaustion/empty, either from over exertion or being low from extended use.  If you eliminate or reduce the drain on the battery, it will bounce back a bit and may turn green.  However I think once you see it turn yellow, it is a warning the battery is close to running out and you should land very soon and fly it easy.  If it turns red you risk a critical battery and a land-in-place or a potential shutdown in flight.  Think of it as a low fuel warning in your car --  the light might come on but the fuel sloshing around might cause it to turn off.  That doesn't change the fact you are about to run out of fuel soon!

If your voltage turns yellow on the way home there's not much you can do apart from just land where you are.  It should still work and you would do well not to push it hard.  It may come on if you are flying home into the wind with a nearly empty battery, and the motors have to work harder than they did on the way out.  You should plan your flights so you fly out against the wind and come home with the wind so you get a "free ride" on return so you have plenty of power in reserve in case of unexpected conditions.  You should not fly so close to empty that the battery voltages are so low and it changes colour.  Did you change the low battery/critical battery settings too low?  You should land with 10-20% battery at least to be safe, don't run it down so close to 0%, it is dangerous and doesn't help the battery at all.  Unless your battery is damaged or has been pushed hard all its life, you probably shouldn't see colour changes when the battery is empty, and you should have landed before the voltage gets that low.

Personal I don't panic when the voltage turns yellow, happens to me all the time. It means at least one cell is at or below 3.6 volts and turns red when down to 3.5 volts. Yellow doesn't mean you need to get right back if the % is still high. But you should be aware you might be pushing it too hard, and need to ease up. Now if the battery % is getting low and you're getting a yellow voltage displayed, that's different and you should be getting back asap. Red is not good at any battery % and getting back to safety asap.