Hello my Friend,
i have great news! :)
After downloading the zip file you provided i succesfully restored the database on my computer with all the data it had contained!
To prove it i can provide these data: the database contains 20 tables (for example: aspnet_PersonalizationAllUsers, dnw_Duikbaarheidsindicaties), 13 views (for example: Bezoek01, dnw_StekAfstanden),a nd tons of stored procedures (for example: ArtiestenVerwijderen, GeefAlleArtiesten).
It contains an SQL user as well with the name of "duiknetwerk".
So pls. let me know if i can help you to restore the database, it would be an honor.