Upgrade from 1.7.a to 2.3: fatal error when enable plugin

[pietrub]

Hello,
I upgrade Phoca gallery from 1.7.a to 2.3 via ftp method, and upgrade plugin by 2.1.
When I enable plugin I have:
Fatal error: Can not redeclare class PhocaGalleryHelper in / home/www/e3819f17a37455b580363a4bcaf22aa8/
web/components/com_phocagallery/helpers/phocagallery.php
on line 16
which abort my site.
Thank you for any help

[pietrub]

Hello,
I found my problem
I copied the folder "front" and not the contents of the folder "front", a problem of comprehension of English read too fast.
Best regards.

[Jan]

Ok