Priority delete

Hi, sorry for my English in the first place. I need help with the following issue: I’m importing xml into my website. Approximately 1500 “products” are loaded into this xml. But I only display 100 of them in xml. I import these 100 into the page (usually there are another 100, as there can be up to 1500 products). Every time I start importing, I also delete old items with the gallery. But there is a problem. Sometimes those items are repeated. When I import new items, they are assigned pictures from old products (sometimes they are the same pictures). These old products and images are then removed after the import. Because these images are attached to some new products, the images are deleted and the products have no images. I would need to set all old files to be deleted first and then import new ones with images, or to duplicate images and not connect to old products so that when I delete old products, new ones will remain with the images. I hope you understand me and can help me .. Thank you