Page gets the Insecure title

As an unfamiliar with Facebook, I made the foll. Mistake :
I opened a new page( photo attached),fr. An existing one.
The new page doesn't allow me to manage it: unable to edit, delete the page, etc.
This stuck me hopeless since I'm absolutely depended on that Add.
I find out that the new page has ,in the right side of the ADD., an icon (close to the star icon)with an Exclamation mark (!). I explored it, and find that it has to do with "SELF-XSS ",which probably has to do with the fact that the page was established fr. Another page.
After 2 month of Try-and-Error,without any assistance fr. Facebook,I choose to take the "insecure" option. The mentioned Icon disappeared ,and along with the page Add. The foll. Appeared (see photo): An red erasure line over HTTPS, and, the red written wards –" insecure" aside the Add.
Anyhow I'm still stuck with the disability to handle the page.