The 24-year-old, who was linked with Southampton in August, has scored three goals in eight league matches this season.
A host of European clubs have reportedly registered an interest, but Jens has claimed that he had 'expected' to leave the club in the past.
"Honestly I had expected to be further in my career right now. But after a bad point and some injuries I had to adjust my expectations. I had in mind that I would have already played tournaments with the Dutch national team and played in a foreign league," Lens told Algemeen Dagblad.
"I play to make a transfer next summer. I will do everything for that this year. I prefer the English and German league as they perfectly fit with my kind of play."
Lens has scored three goals in five games for the Netherlands.