Can´t get all tweets

Hey!
We are two students currently writing our bachelor thesis in social sciences - out knowledge in python is therefore rather limited. For this we successfully collected twitter data using the got-script.

We have collected data using the hashtag hurricaneharvey for the days 25th of august 2017 and the 29th of august 2017.

Unfortunately this did not collect all tweets - some hours are always missing. Is there a fix for that?
Or is there a way to collect tweets on a specific day in a specific time frame (ex: (8am till 12am)?

thanks a lot for your help in advance!