Sad but true.A regularly asked question that has no foolproof solution. No matter what precaution you take, if you park it at the same location at the same times daily, it will almost certainly be stolen. Bicycle thieves do sometimes use vans to carry off bikes so only have to detach from street furniture.
The best you can do is double lock to a secure stand etc using two of the best D locks or a D lock and a very strong chain lock. Then that should be at varying locations in the area, and the locations are best if always busy with people. Removing the battery is also an added security measure to make the bike less attractive, and removing the saddle/seatpost as well is even better.
But nothing gives 100% protection, so insure as well.