Update codeigniter

Must i upload other folder to upgrade or only  vendor ? I leave in server old vendor folder renamed vendor_old if i change vendor with  the old vendor work ....

On locale i have system folder in server  no why ?

You must upload everything, or else it won't work.  Why you don't have a system folder on the server, is a good question.

To be sure i upload on server system folder too ( same problem) , without system folder on server and older vendor everything  work....