Denti,
Lohn- und Einkommensteuerberechnung would disagree with you. As you qualify for the 16,4 % Schichtzulage (tax free element due to working nights and holidays), a gross pay of around 8,300 €/month should give you around 5,000 € net.
I have no idea what an FO contract in Germany would pay as none exist so far. Only for SFO. On that you will gross around 100 k/year.