Is it possible to still live in a world war 2 bunker today after it’s long been abandoned?

Possible but not advisable. After 80 years in an abandoned state, the bunker will likely be filled with dangerous mold. If you OWN the abandoned bunker, you can hire a mold mitigation company, and have that corrected, and add new insulation and new drywall.

If it is relatively intact it can work.