from 4000 gross, you would have around 2900 net after taxes and all social insurances. If you are planing on living in a big city like Berlin, Munich, Hamburg, etc. the apartment rent would be around 1800 Euros per month (all bills inclusive). For food, groceries around 500 Euros per month for both, then for internet bills, mobile phone bill, transportation tickets it would be around 100 Euros per month. So you would have around 500 Euros left for everything else per month. Not gonna lie, that's gonna be tough. It would be more like on survival mode rather than living a comfortable life.