Hi Rolf,
The red button is at the far right end of the line, and your screenshot is cut just before that column. Only a customized file has it, so on the seven lines of your screenshot there is nothing to remove: on a customized line you would see two buttons at the end, "Änderungen anzeigen" in blue and "Anpassung entfernen" in red.
Instead of searching for a file name, use the "Template" filter at the top of the Display > Views page and select your template, tp_artist. Every line which shows those two buttons is a customized file, and those are the only ones to look at.
One warning about your second screenshot: that is the edit screen of product / listing_img.php. If you click Save there, a customized copy of that file is created, even when you changed nothing at all. As long as the file does not exist, the line "Pfad der Überschreibungsdatei" ends with "(wird erstellt, wenn Sie Ihre Änderungen speichern)". Leave that screen with Abbrechen, not with Speichern.
I looked at your website again just now :
- the products listing is back to the original layout of HikaShop, with the image, then the price, then the name. So that removal worked.
- the product page is still customized. The image is still in the right column and the left column is empty, which is what stretches the page. So product / show_default.php still has its copy, and that is the one left to remove.
About the landing page, one thing worth checking : removing a customization deletes the file for good, there is no backup of it. If your template tp_artist came with its own version of that view file, then the drag and drop editor overwrote it the day you saved, and removing the customization deleted the version of your template along with it. The page then falls back to the standard file of HikaShop, which does not have the same order. If that is what happened, installing the tp_artist package again on your site puts the files of the template back, and does not touch your content or your settings.
Can you tell me which page you call the landing page, with its address, and what is different on it compared to before ? The page at megakit.de/de/ is a Joomla article, not a HikaShop page, so the views play no role there.