Twitter is 100% public. Anyone with an internet connection can see your Tweets, whether they have an
account or not. If you want only your followers to see your timeline, all you have to do is protect your Tweets.
If someone has posted any of your private information, or an intimate image without your consent, and refuses to remove it then you can file a report. For information on how to do this, you can access a guide here: https://support.twitter.com/articles/15789
How to Block Someone?
Search for the person you wish to block,
Next to Follow you will see either 3 dots or a cog icon,
Click this then select Block@(person's name)
This information is up to date as of 28th March 2019 and will not be updated soon