How much does a PhD cost?
German universities do not take any tuition fees, apart from the semester contribution and public transport ticket (about 300 EUR per semester (October-March, April-September).
Living and accommodation expenses are about 1,000-1,200 EUR monthly.
The rent in Berlin has risen extremely to about 700-800 EUR and more.
Food and leisure should be about 300 EUR monthly.
In addition, you should have health insurance (about 50-250 EUR monthly, depending on the insurance provider), and liability insurance (starting from 20 EU to about 50 EUR annually).
Also do not forget that you will need to be able to apply for or probably save up for expenses for resources, materials, fieldwork, travels, conference, papers, publications, and also electronic devices (laptops do not live forever).
A scholarship from funding institutions may only just cover the living expenses.
If you cannot fund your PhD, consider all risks of a 4-year procedure before embarking on the journey.