Splitting PNR with Lufthansa airlines: any tips or advise?

Hello, me and my friend booked a flight together, but due to some changes in our schedules, I will be traveling two days later than him but return back on the same day. So the only option for us is to split our PNR into two separate bookings. I hope this is allowed with Lufthansa Airline.

In case the bookings get separated, will the counter ask for proof of the credit card used for the booking? How does this process work? This is my first time traveling with Lufthansa airline, so I'm a bit curious about how it all goes.