I hope you can clarify for me the reality or the method of understanding the hadith about the suckling of adults?

The Hadith about adult suckling is authentic, but it is specific to Sahlah bint Suhayl and Salim (may Allah be pleased with them both). It was a special dispensation from the Messenger of Allah (peace be upon him) for Salim alone. The majority of Muslim scholars and the four Imams have concluded that suckling by an adult (one who has exceeded two years of age) does not establish mahramiyyah (prohibition of marriage). They interpreted the Hadith as either being specific to that case or abrogated.