Hello mehmetduhan,
Thanks for reaching out on the Apple Support Communities. From your message it sounds like you have some questions about using a third-party USB-C power adapter.
This article will provide you with information on how you can use the USB-C power adapters with your iPhone 8 for fast charging: Fast charge your iPhone and iPad - Apple Support.
In the article, it states you can use, "A comparable third-party USB-C power adapter that supports USB Power Delivery (USB-PD)."
For the specifications of the Spiegen charging adapter, you'll want to reach out to them directly: Something You Want | Spigen– Spigen Inc.
This article will provide you with general information about third-party accessories: About iPhone, iPad, and iPod accessories - Apple Support.
All the best.