How to replace field values ​​in init.php when uploading from 1C to Bitrix?

Question

1C-Bitrix

Good day. The question is that I need to write "Full name" (from 1Ski) in the property (id=C1_NAME) of the product, since "Full name" overwrites the announcement of the product and this is a necessity.
I wrote the following in init.php:
AddEventHandler("iblock", "OnBeforeIBlockElementUpdate", "DropPreviewText");
AddEventHandler("iblock", "OnBeforeIBlockElementAdd", "DropPreviewText");
function DropPreviewText($arFields)
{
if (@$_REQUEST['mode']=='import')
{
if($arFields['IBLOCK_ID']==5 && strstr($_SERVER['REQUEST_URI'],'1c_exchange. php')) {
$arFields['C1_NAME'] = $arFields['PREVIEW_TEXT'];
}
}
But it doesn't work.
When unloading, the information of this property successfully changes to a new one (which was set in 1C) and is also present in the unloading files (which means it unloads with a bang and this is not the problem), but how to access the property and change the value before the Full name is deleted and the goods are recorded ...

Answer 1

When unloading from 1C, you can only process data after unloading using
AddEventHandler('catalog', 'OnSuccessCatalogImport1C', 'customCatalogImportStep');
Here is an example
I was also looking for tried other events. TP just said