@Diego2395
The "new host" promotion is a 10% discount offered on new listings. You can also offer 10% discount yourself. It resides (as any other promotion) in the promotion section of the listing and can also be turned of. If you unlist a listing, current and future reservations remain active. Some hosts use two identical listings to have opportunity to set different prices for the high/low season, each listing only have calender opened for that season etc. .
If no special purpose for you, then delist the "old" listing to prevent double bookings.
https://www.airbnb.com/help/article/476