How do i flash twrp on a samsung device without getting replaced by the stock rom

I do not repeat the question on the title, I wanted to flash my a15, format data using the twrp but when i boot into the system and back to the recovery, it goes back to the stock.

How do yall make the twrp presistent and doesnt get removed by the stock rom?
Is theres an other way to patch the twrp without installing magisk?

thanks, answers will be appreciated.