Thanks for reply Rashida, but nothing changed....
Of course, when I try to edit addon on Page "Strona główna OLD" > Section Logo> Text Addon I can edit like you.
Next I press "Save" on top.
After that changes are made, but... When I open Page again all changes disapear.
On your screencast you didn't back to edited page to check is changes are saved.
When you will try to check, keep in mind that Page "Strona Główna OLD" is set as hidden position in menu.
Please don't change anything on other pages.
Next please try to change addon name from "Text block" to other name.