Sorry for answering in English:
You can update from 1.8 to 17.1, but to do so you need to install the regular 17.1 packages, plus the compatibility packages (egroupware-epl-compat rpm or deb package or egroupware-epl-contrib archive).
This is necessary as they contain the database schema-upgrade scripts from 1.8!
Recommend way is to make a new (package-)installation eg. on Ubuntu (see our install instructions on https://wiki.egroupware.org), install the additional egroupware-epl-compat package (!), rsync the files directory (/var/lib/egroupware/default/), backup EGroupware in Setup of old machine and restore in Setup of new machine.
We (EGroupware GmbH) have special packages to assist you with the update, including a short workshop to inform you about what’s new in the new version: