The 18:12 trip leaves only 3 min to change from Limpertsberg, Crispinus to Pfaffenthal-Kirchberg, Gare (2 min walk); a delay could make you miss line IC.
Direct option
The direct 18:07 departure takes only 4 min more and has no change.
1st class
1st class on trains is not free; buy a 1st-class ticket (CFL app or ticket machines) before boarding.
Free travel
Public transport inside Luxembourg is free since 1 March 2020: buses, the tram and trains in 2nd class need no ticket.