TootsieTails

From what you wrote here, I'm having trouble understanding which part of the process you are going through, and which package is possibly missing. Are you doing the K-3 or the CR-1 Visa? I wasn't sure of that either from your question, so I wanted to make sure that you know which one we are doing in case yours is different. We are doing the CR-1 Visa, as we are already married. I have no experience with the K-3 Visa application process, and this is just our experience, so everyone has a different timeline, so a slightly longer time wait could be totally normal. 
 
Marriage: 1/15/2018 Mailed I-130 package: 2/5/2018 Received NOA1: 2/13/2018 Received I-130 Approval: 3/24/2018   Since we are applying DCF with Frankfurt, we received a mailed letter from Frankfurt about one week after the letter with the I-130 Approval. The I-130 approval date was 3/24/2018.    This letter from Frankfurt arrived on 4/7/2018, and the date on the letter was from 4/4/2018. This mailed letter from Frankfurt contained our case number. The mailed letter from Frankfurt was directing us via a link to the website of the US Embassy here in Germany, where you could find all the application instructions. Specific directions in the letter said documents submitted by fax or e-mail would not be accepted.    Reading through the instructions, we were directed to complete the DS-260 (online) and fill out our mailing information with where we wanted our Visa packet mailed upon completion (a URL/link was provided for this). In addition, the link to a checklist with the required documents- and where to send them- was provided.    We completed the online portion, which was the DS-260 AND entering the mailing address for our Visa packet, on 4/9/2018. We mailed the requested documents on 4/10/2018.    On 4/13/2018, we received an e-mail from Frankfurt directing us to schedule the medical exam. We followed the directions provided in this e-mail for the medical exam. Later on the same afternoon, we received another e-mail stating our request for an appointment had been approved, and we could schedule our own appointment online by following the directions provided in the e-mail. The appointment was scheduled for the interview, which will occur on 4/24/2018.   Hope this helps.   
 
 
 
 
 
 

We are DCF Frankfurt also. Feel free to check out our timeline to see how long it has taken us, filed the I-130 in February, we now have an interview date (towards the end of April). 

All your questions can be answered by reading through the following links:
 
From Official NVC's websites click here
From Visa Journey Wiki click here 
 
Once you're done, read them one or two more times to really understand it. By doing so you will become a master of the entire process 
 
Use the Document Finder tool here for U.S. Visa: Reciprocity and Civil Documents by Country and select the country that issued your civil document.