menu dissapeared

hello,

When i change category and placed on top it works.

But after 20 minutes the category menu is dissapeared, and when i again change setting on category, its back and after 20 minutes its again gone

Your question makes no sense. Please provide more information. And what opencart version do you use ? Maybe an error log from opencart as well as the error log from your hosting server will help.

Maybe one place you can start checking because you said after 20 minutes is your cron jobs that might change something in your database ? Or a cache service that gets restarted etc....