Hello,
first of all, you should tell us the current version of your shop. I guess it might be 3.5.6 or 3.5.7, because this is the minimum required version for an update to shopware 4. As already described, it is not possible to update diectly to shopware 5.2.9. The workflow to update from shopware 3.5.x to 5.2.9 is:
3.5.6 to 4.1.2 (Update-Script)
4.1.2 to 4.2.4 (Manual update with the update package)
4.2.4 to 5.1.6 (Manuel update with the update package)
5.1.6 to 5.2.9 (Auto-Updater)
With the release of shopware 5 the support for shopware 3 is outdated, so there is no supported update-path any more. But you can use „the old ways“, they should still work.
You can find the updater to 4.1.2 here: http://releases.s3.shopware.com/updater_4.1.2.zip
The package should be unzipped to an folder „update“ and uploaded to your shop folder. Afterwards you can start the update by opening www.mydomain.de/update.
There are a few bugfixes for the script that you should add to the source code. Please see: Shopware Issuetracker
Change update/libs/Shopware/Update.php in row 937:
if (count($deltas)) {
to
if (is_array($deltas) && count($deltas) > 0) {
Add after row 2251:
if(is_array($product['attributes']['shopware_compatible'])) { $product['attributes']['shopware_compatible'] = end($product['attributes']['shopware_compatible']); }
The critical update will be 3.5.x to 4.1.2, because with shopware 4 the whole variant logic has changed and the updater does some „magic“ stuff to apply the new structure. When the step to 4.1.2 is successful, the next step will be very easy. The update-packages from 4.1.2 to 4.2.4, 4.2.4 to 5.1.6 are on our download page: http://community.shopware.com/Downloads_cat_448.html
Moritz