Broken site after upgrade

hello I just tried to upgrade from kirby 3.5 to
I deleted the kirby folder and uploaded the downloaded one. I used sftp and got no error during the upload
i get this error :

Call to undefined function page()

same error for snippet() and every kirby function

where should I investigate ? thanks in advance : )

The release page has a list of all breaking changes. It is generally not recommended doing updates on a production server without having tested locally, the less so when an update contains breaking changes, as in this case.

If you are using plugins, you will also have to update affected plugins.

thank you i going to remake my whole project from scratch ^^