The message "String or binary data would be truncated" is a database server message that simply means that the data you are importing is too large for one of the table fields. dbFront also let you know that this happened on the very first row of your CVS file.
The two possibilities are that the data is just simply too long, or that the data is being imported into the wrong field.
Since this is a database error, dbFront will have logged the entire SQL and error message in the Logfile for you to examine and debug. The Logfile can most easily be accessed by opening [Help] \ [Log Viewer] and searching for your error message in the bottom log.
NOTE: A related bug was fixed in dbFront version 18.104.22.16801.