The Czech driver raced in Italian and German F4 as he adapted to competing in junior single-seaters, having only started racing at the start of 2017.
He comes into a second season of German F4 on the back of a successful winter campaign in UAE F4, finishing third in the standings with one win and six podiums in the same Tatuus-Abarth F4 car he uses in Europe.
The 18-year-old German took three wins, five podiums and three pole positions in the 2017 championship and will be confident of building on that this year.
As well as racing in Germany, Lirim gained further experience of the Abarth-powered F4 car in Italy where he gained another two podiums.
Introduced by the FIA in 2014, Formula 4 is designed to allow young kart racers the perfect way to experience driving a fully-fledged racing car within a reasonable budget.
Charouz Racing System is collaborating with US Racing to field a pair of F4 cars in the ADAC F4 Championship and selected rounds of the Italian F4 series.
Designed by Tatuus and powered by Abarth, F4 is the first step on the single-seater ladder.