Private leasing car

With 4K€ netto salary (+around 3k€ from my gf), -1.5k€ rent, 500-700€ general expenses per month: what would be a reasonable upper limit for a monthly private leasing contract on a car. I will need the car for my job, but my employer wont organize it for me. They will give me 40 cent per km. I expect to do around 20k km per year, with 10 of that being private use.

I got a quote for 600€ a month from the Cupra garage, not sure what to think about that. Looking for some advice here.