in the Kiddush of Shabbes night there are 2 berakhots, Borei Peri HaGafen and Mekadesh Ha Shabbat , after Borei Peri HaGafen I drink the wine, or just after Berakhot Mekadesh Ha Shabbat ?
We don’t drink until after finishing mekadesh hashabbos. You are bringing up a good point, why is it not considered a hefsek (a break) between the hagofen and drinking? The answer is that since we are drinking the wine because of the kiddush, and a way of honoring the kiddush, therefore the kiddush is not considered a hefsek. Additionally, we are not allowed to eat or drink before saying kiddush. Therefore, because of these reasons we drink the wine only after finishing the whole kiddush.
Brachos 51b, Rambam Shabbos 29-7, O:CH 271-4, 10.