Stationarity issue in time series data

I have time series data (Number of malaria patients) consists of 125 sample observation.

I am going to apply ARIMA model.

When I check stationarit the series is non stationary.

I take first difference the series become stationary but the issue is that when I plot ACF or PACF for stationary series (1st difference) the ACF or PACF at lag 0 is 1.

Check the attach file. Please let me know how to handle this issue?

Thanks in advance