Cannot install created module

[stevstrong]

Hello, I followed your online course on Youtube and tried to make the steps indicated there. I have locally installed ODOO 14. I have checked out this repository branch 14, commit 3d0a7d7 into the folder "C:\dev\Odoo\server\odoo\addons\plant_nursery". This is the file structure:

I launched ODOO and did find the new app, but when I tried to install it I got the following error message: "User error: You try to install module 'plant_nursery' that depends on module 'documents'. But the latter module is not available in your system."

See attached picture. What do I miss here? How can I install the module error free?