I can’t turn off incognito mode

In Chrome? If so, see the following from https://support.google.com/chrome/answer/95464/navigare-in-privato-computer?co=GENIE.Platform%3DiOS&oco=1

Close Incognito mode to stop private browsing

Incognito mode runs in a separate tab from your normal Chrome tabs.

If you have an Incognito tab open and you open another one, your private browsing session will continue in the new tab. To exit Incognito mode, close all Incognito tabs.

1. On your iPhone or iPad, open the Chrome app .
2. At the bottom, tap Switch tabs . Swipe right to see your open Incognito tabs.
3. Find the tab you want to close. At the top right of the tab, tap Close .

or if you mean private browsing in Safari, see the following from Turn Private Browsing on or off on your iPhone or iPod touch - Apple Support

How to turn off Private Browsing

1. Open Safari on your iPhone or iPod touch.
2. Tap the new page button .
3. Tap Private, then tap Done.