My realm has already expired, even so I want to continue using the world, the good thing is that there is the option to install it, but when I select the install button it turns out that I do not have space in my storage and that is wrong, because I have more than 20 gigabytes free.
Instructions:
First I enter Minecraft, then I enter to edit my realm, after that I select the world, and finally I click on the button to download world but it says:
"You are almost out of data storage space! Minecraft has restricted access to this feature until you clear up additional space."

Clarifications:
-My console is a nintendo switch.
-Game in digital format.
-I already tried clear up some space.
-The world weighs 915.16 MB.
-I have around 20GB to use.

Well I hope they help me, because I have not played since then because I love that world.