GM says it can tow 4,850lbs...
http://gmauthority.com/blog/2017/08/2017-opel-insignia-sports-tourer-can-tow-up-to-4850-pounds/
GM says the Euro version can tow that much. The US version is 1000 lbs.
If you tow over stated capacity and have an accident good luck with your insurance covering it.