Hello my fiancé had his interview in Frankfurt last month. By the time we got our interview letter he submitted his ds-160 form online and it took a week to get his interview. Before that he had already done his medical two weeks before he got his letter and sent all needed documents to Frankfurt. Once ds-160 was submitted he mailed them in the post when to have his interview. A week later he emailed Frankfurt as to when his interview was and they told him and it was 5 days later. So after you submitt that form and send all needed documents email Frankfurt with name and case number and ask if they have all documents needed and they will email you when the interview is good luck! <3