6 days ago by
I assume you are talking about the Main instance at https://usegalaxy.org. My answers reflect that. Other Galaxy deployments will have different setup.
When I upload my data am I the only one who has access to it?
Technically no. Data is not encrypted so people with access to the hardware could access it and also Galaxy Administrators have means to access your data. Furthermore depending on protocol you use it might or might not be encrypted during the transfer (http vs https, ftp vs ftps)
Can I delete it permanently whenever I want?
edit: if you have very sensitive data I recommend using local Galaxy (http://getgalaxy.org) and possibly using the pre-configured docker image