Hi
When defender real time is turned off after a while it will automatically restart. The best way to disable defender used to be done in services but you can't do that now as you can't access any controls they are all greyed out, apparently a deliberate act by Microsoft in their never ending crusade to force their security ideals whether you want them or not. However having said that Defender is adequate for many users and it's built in and free so it's not forever bombarding you with ads, and it will run in unison with other anti malware such as Malwarebytes.