Disable Huawei P20 monthly data limit?

I have a Huawei P20 with Android 9 and have entered in the settings for data usage / More data settings a monthly data volume. I would like to have it out again. If I want to delete the data limit out, you can't press OK.

How do I get the data limit out without having to reset the phone? In the Internet, there's the instructions only for Android 8, because you could clear the cache in the phone manager and then the data limit was gone.

Clear cache and entire data then it is gone

Unfortunately brings nothing there was only on Android 8

Can't you simply set the data limit back to unlimited?

Otherwise, try it under Intelligent data consumption optimization if you can switch it off or set otherwise

Unfortunately it does not work either

find optimizer application on application settings then clear data from there, works 100% on huawei p20 lite