How could I improve my FB Prophet forecast?
Data here is bit noisy &amp; has a lot of fluctuations. As few comment suggest apply some transformation on it. I would say get your data in some smaller range &amp; then apply LSTM to predict it. I made time-series work with LSTM with removal of noise by eliminating outliers &amp; it worked with nice further prediction.

RNNs tend to work better with time-series data especially bidirectional-LSTM due to their backwards learning capabilities.