Videos usually go viral, because they motivate people to share it. This can be due to the fact that the video makes them feel a certain way. If the video makes them feel angry or sad or makes them laugh or feel inspired, then they will feel motivated to share it. Trends and current events (like the mid-term elections or trending hashtags) also impact the amount of views a video gets. So my advice would be to include in the video (or the caption): something related to current events in Germany (whether it be something humorous or scandalous.)
Feel free to contact me for examples.