What will the coriander, cumin and paradise add to the lentil soup and can I do without the paradise?
Coriander, toasted cumin and grains of paradise all are spices. 

Grains of paradise being the more uncommon spice is similar to black peppercorn and was historically used as a substitute.

They play the role of what spices commonly do which is flavor your lentil soup. Without it, it will just taste different than the recipe intended.

If you cannot easily get a hold of grains of paradise then just use ground black pepper as a substitute.