Well I will answer in English but assume your are Dutch.
1. Select by expression: Depence on the data set of the shapefile, and if the line as draws is very strick. If it is than it is not the best option.
2. Select by Polygoon: Is the line is very strick, make a polygoon from the part to don't want and select what in the polygoon. By turnaround selection you have to Northen part of The Netherlands.
Importent is if the shapefile data is a polygoon, so if there is data which goes through is line does is count or not?
Tip 1: In the attribute table there is above in the menu the option, turnaround selection (selectie omdraaien). Thise is very handy tool!
Tip 2: I think to data set it's large (Netherlands is a large country), so to reduce calculation time of your PC you can make a new shapefile of the selecting the shapefile in the panel and save, with the option: Only save the selected data.