The cost of living in Dusseldorf can vary depending on your lifestyle and needs, but it is generally considered to be on the higher side. As an intern, you can expect to spend around €800 – €1000 per month on accommodation, food, and other living expenses. However, there are ways to save money, such as sharing a flat with other interns or taking advantage of student discounts.
Room in shared apartment: €600 – €900
Eletricity: €100 – €200
Phone mobile contract: €30 – €50
Internet: €30 – €50
Groceries: €150 – €300
Eating out: €80 – €200
Transportation: €80 – €100
For more specific information, see this source.