Concatenating two fields (Lookup field + Text Field into third filed)

Any particular reason you're trying to use an IF statement? If you're just trying to concatenate you just need to do the following as one example: 

[Project Name] & "-" & [City] 

The If statement would only be needed if you had something like different project name fields or different ways you wanted to display the string based on customer or some other factor that you might combine different or more fields in the string.