One Button WS2812b

Hi,
I'm new in Arduino - Projects and i found a great code for WS2812b https://www.hackster.io/Oniichan_is_ded/neopixel-x-arduino-x-button-c26e9a
Unfortunately i stock in case9 and can't go back to case0. Is it my fault? Or could somebody help me? Would be appreciated!

Is it my fault?

Yes. You have uploaded the coded, so it is your fault.

theaterChase is called 10 times:
for (int j=0; j<10; j++) { //do 10 cycles of chasing

so either wait until it was done 10 times or reduce the iterations to 2.
for (int j=0; j<2; j++) { //do some cycles of chasing

P.S. please check your auto correction, it makes your post barely readable for non-native speakers.

it makes your post barely readable for non-native speakers.

I can tell you that native speakers really struggle with that as well.

What happens if you keep your finger on the case 0 button for a long long time?

and i found a great code for WS2812b

No not great code, quite poor bad code.
Hackster, while not being as bad as instructables, still has no quality control. So anyone can post anything without scrutiny.
This is what we call blocking code, because your button is blocked from being looked at until the whole animation sequence is finished. If the button is not being pressed at that moment then it whips round and does it again, so keep your finger on another pattern button for a long time, and it will eventually change.