Does anything arise from my joking with the seller who expressed his desire to marry my daughter, and my agreement to this joking by saying: "Yalla shil" (Go ahead, take her/him)?

The conversation that took place between you does not constitute a valid marriage contract (nikah) nor does it entail any consequences. While a marriage can be validly contracted by someone joking, this is contingent upon the fulfillment of its pillars (arkān) and conditions (shurūt), including the formula of offer (ījāb) and acceptance (qabūl). One should avoid jesting in matters of marriage; it is a solemn covenant that should not be subject to frivolity and joking. Sheikh al-Islam Ibn Taymiyyah said: "The Lawgiver forbade taking the signs of Allah in jest, and that a man speaks with the signs of Allah, which are contracts, except with seriousness, intending their legal implications. For this reason, jesting with them is prohibited."