I'm sorry but it is difficult to understand exactly what your question is.
IOS 27 update is not delayed. Many people are successfully updating their iPhones. If some apps are not opening quickly or at all, it could be the developer has not updated the app for the new iOS yet.
Could you please separate this phrase into separate, complete sentences so we may better understand?
"open any app it’s take 3 to 4 seconds even when someone call it’s same white background and 3 to 4 second the call will show any answer for that how to fix this bug issue "
If English is not your first language, you may find one of the links in the page below helpful.
Links for Apple International Support - Apple Community