Writing a plugin for WordPress

I am looking for a person / agency to make a plugin for me under WordPress:

Scenario:

A solution for a photographer to sell photos to clients: the photographer, after the session is finished, adds to a subpage dedicated to the user. The photos go to the gallery appropriately resized and watermarked with the selected watermark. The user adds photos from the gallery to the shopping cart on a select basis. Here, the necessary ability to freely set thresholds and prices. For example, after adding 5 photos at 200zl each, the next ones are at 100zl each. - Nothing rigid - we can not determine the prices or thresholds - it must be easily set manually when adding images for each gallery separately.

In the column on the right is a classic summary of the shopping cart, i.e. photos added and the total price summed up.

After payment to the customer to the indicated on the checkout automatically go to the higher resolution images without the watermark.

It can be WooCommerce because of the ready-made solution in the form of a shopping cart / checkout / payment - but absolutely not necessary.