You are adding a formula to a field called "Content". The formula is referencing itself.

If you already have a field "Content" containing static data, and you wish to use a formula to extract data from it, you must do this using a new field, e.g. "Content 2". You can then delete the previous field and rename the new field in a 2nd Field Organiser block.

Thank you so much ^-^
Just figured it out that I do wrong thing - -'