Hi I was in Frankfurt as well they asked for my fiancés recent W-2 and the IRS tax return they didn’t need any bank statement, employment verification or any other tax documents. I think it’s good to have them but all they asked about are the mentioned above documents and the I-134, my birth certificate, my police certificate, and asked if I had a visa already and if it’s still valid. I believe that’s it 😄 it’s always good to have more but it’s really important to have what they request good luck 🍀