Is it possible that the repairs part having the same lifespan ??

I don't know if Apple still offers battery replacement service for the iPhone 6s – but you could check.

Batteries - Service and Recycling - Apple

iPhone Battery Repair & Replacement - Apple Support

You'd have to ask Apple about whether the replacement batteries they install have the same capacity as the original ones.

ngote Said:

"Is it possible that the repairs part having the same lifespan ??: Hi ! I’m have a question: But is it possible to do a battery’s remplacement and get the same results as genuine the iPhone came with?"

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Get a Genuine Battery:

It it is ungenuine, then you are going to get an error that won't go away. It will not leave your screen, essentially making it a brink and oh so hard to work with. So, get a genuine battery, by all mean necessary.

Where to get a New Battery:

Getting a New iPhone Battery:

Contact Apple, and setup a Genius Bar Appointment or see an AASP (Apple Authorized Service Provider) in your local area. Be wary as to where you get this item, ask you may get an error of an ungenuine battery. So, to avoid this continual message, it is best to have an Apple or an AASP replace the battery. So, where to get a new battery:

A. Apple Contact Info:

• Contact Us - Choose Locations
• Proceed from there, as necessary
• Why the Wait: Phone calls are taking a bit to go through at the moment, due to lots of calls. With the Coronavirus Pandemic, many are at home at the moment, with much time on their hands to contact Apple. So, just stay on the line, and you will get through :) 

B. Contact an AASP: 

1. Go Here: Find Locations - Apple Authorized Reseller
2. Click: Service & Support
3. Enter: your location information
4. See: if there is an AASP nearby
5. Contact: an AASP that shows up, and find out more about the services that they offer to fix the battery