Try the following and see if either of those answer your extended questions:
My city: `= this.City`
or: `= this.city`
Last city: `= this["Previous city"] `
or : `= this.previous-city`
File title: `= this.file.name `
Composite: `= this.file.name + " – " + this.city `
The documentation on Field names could also be well worth a visit, to understand what’s happening. (Or doing `$= dv.span(dv.current())`
in a note where you wonder what is defined or not)