Complex sentence: On 26 May, he scored his first international hat-trick in a pre-tournament friendly against neighbouring Luxembourg; however, as Belgium made seven substitutions during this match instead of the permitted six, it was not recognised as an official match by FIFA.
Split into simpler sentences: On 26 May, he scored his first international hat-trick in a pre-tournament friendly against neighbouring Luxembourg. However, as Belgium made seven substitutions during this match instead of the permitted six, it was not recognised as an official match by FIFA.