how i can add a certain value to all my products price in the store at once
Do you mean like adding $10 to every product price?
yes
This post might be useful for you.
Hello,
My name is Alison, I’m the Customer Success Specialist for Ablestar Apps. I’m sorry for the late reply on this, but our Bulk Product Editor app allows you to easily modify the price in a number of different ways, and you can adjust the compare at price at the same time if need be. This document will walk you through the process, https://support.ablestar.com/article/27-your-first-bulk-product-edit.
Another advantage to using the app is that you can also ‘undo’ edits. This is especially helpful when setting up sales, as you can just ‘undo’ 'the edit when the sale is over.
If you have any other questions you can reach out to us directly at support@ablestar.com.
Best,
Alison