Hello,
I want to change the price when the user selected the subscribe and save button
gif bellow is just a example.
You will need to be much more specific. This is an advanced issue with many moving parts and answers that vary wildly among themes.
You have to find the current javascript events and functions handling this and customize them to have the business logic you need.
If you have coding experience start here https://shopify.dev/themes/product-merchandising/variants
https://shopify.dev/themes/pricing-payments/discounts
https://shopify.dev/themes/pricing-payments/subscriptions/selling-plans
Merchants that need to hire advanced customization support can contact me at paull.newton+shopifyforums@gmail.com with details: store-name, storefront password,theme name, link to their post , and use case details.