This is the 10047th most frequent Polish word.
belgijskim
"Belgijskim" means "Belgian" (describing something as relating to Belgium) in the instrumental case in Polish.
The word 'belgijskim' refers to the nationality or country association of the train, specifically that it is Belgian in origin.
Podróżowałem belgijskim pociągiem do Holandii.
I traveled by a Belgian train to the Netherlands.
In this case, 'belgijskim' describes the nationality of the chef who prepared the dish.
Zamówiliśmy belgijskim szefem kuchni przygotowane danie.
We ordered a dish prepared by a Belgian chef.
Here, 'belgijskim' refers to the origin or characteristics associated with the education system of Belgium.