we do not share your data with anyone and there are many ways to control the visibility and storage life of your data here.
but the internet is a public space and you should always assume your data could be compromised.
be smart with your password, use tor or a vpn, and use pgp for sensitive communications.
Lots of apps leave a legacy of activity, clean that shit up!
Open Terminal found in Finder > Applications > Utilities
In Terminal, paste the following: defaults write com.apple.finder AppleShowAllFiles YES.
Press return. If theres no error you are done with the terminal now.
Hold the 'Option/alt' key, then right click on Finder in the dock and click Relaunch.
There is a library directory for the mac itself and your user.
Now check the subfolders for application remains and delete. Here is list of the most common relevantt directories. ~Library > Application Support ~Library > Caches ~Library > Logs ~Library > Preferences ~Library > Containers ~Library > Cookies