error on line 4 at column 81: xmlParseEntityRef: no name

I have installed it now,
https://rausch.it/feeds/XMLGoogleMerchantSource.xml
but it doesn't work and the following error message appears:

This page contains the following errors:
error on line 4 at column 81: xmlParseEntityRef: no name
Below is a rendering of the page up to the first error.

Please, your version of LiteCart and PHP...

Please, your version of LiteCart and PHP... and The name of your website ?

I wanted to let you know that I have sent the corrections to your email address

My LC version is the 2.5.5, PHP 8.3
working with a custom template:
https://rausch.it/includes/templates/255.catalog/css/custom.css

I replaced the file with the one you sent but the error still persists:
https://rausch.it/feeds/XMLGoogleMerchantSource.xml

error on line 4 at column 81: xmlParseEntityRef: no name
Below is a rendering of the page up to the first error.```