Интересно а у нас «ты знаешь »)

Да не заметил. Обычно это "you".

(Before a surprise party)
A: You stand over there and turn off the lights when Becky’s walking down the hall towards the apartment.
B: How do I know?
A: I’ll give you a thumbs-up when I see her coming.

В этом случае просто "(А) как я узнаю?"

The key here is the use of the plain present (how do I know) instead of the future (how will I know). The use of the plain present indicates an assigned duty. We have two examples of it in my snippet: (1) you stand (your job/duty is to stand over there); (2) (how do) I know (=when it’s time to do my “job”).

Да, тяжелый случай...
настоящее время это будущее, а будущее это неопределенное.

Yes, when we talk about our roles in something, we use the present to refer to the moment when it actually takes place. For instance, when rehearsing a wedding, we’ll often tell everyone where they’re to stand using this present - especially if it involves movement: “When the bride walks in, you move to this side of the altar, and you stand behind him.” Then someone else could ask, using the same tense “And where am I during all this?” (=where will I stand?)

В этом случае в русском так же.

👍🏼

Однако, "How do you know that?" = "Откуда ты (это) знаешь?"
Да?

да

👍