Dealing with time series data which has multiple observations for the same timestamp

I have a time series data in Python 3 as follows:

Date                Weekly_Sales
2010-05-02              3400
2010-05-02              5600
2010-05-02`             4590
2010-05-02              5800
2010-05-12              2380
2010-05-12              6700
2010-05-12              3700

The time series is not continuous as there are multiple observations of the same date.I'm trying to forecast sales in python using ARIMA but my ACF and PACF plot shows that there is no corelation between the lags.Also if i run the dickly fuller test to test stationarity,my system freezes.

How can I fix this?