11.3 GB is the compressed file to download.
But you will need an extra 15-20 GB at least to uncompress.
Plus a lot of GB to install.
All in all, you should have at least 50 to 80 GB available to install new version.
That's a lot effectively.
You could try to download from here:
https://developer.apple.com/download/more/
It requires usually a little less disk space.
Topic:
Developer Tools & Services
SubTopic:
Xcode
Tags: