How can I extract Google analytics data?

I have the client_id the client_secret, the authorization code, but how exactly can I extract data from google analytics. In which format do i have to enter startDate or the endDate?

Mein Code bisher

access_token='XXXX';
headerFields = {'Authorization', ['Bearer ', access_token]};
options = weboptions('HeaderFields', headerFields, 'ContentType','json');
webread('https://www.googleapis.com/analytics/v3/data/ga','ids=ga12345',...
    'start-date=2018-12-01','end-date=2019-01-31','metrics=ga:sessions', options)

Unfortunately, the in 2016a the HeaderFields cannot be added into weboptions, any workaround?