"I don’t know that they’re going to be able to help us"
Uly, this sounds like "Я не знаю о том, что они стремятся/хотят нам помочь", or I don't I understand something... Could you please explain?

We use that when we doubt someone’s ability to help us knowing what we know.
Adam: I’m at the end of my rope. I haven’t worked since lockdown and my car just broke down. I need to start work next week and the mechanic wants $500 to get my car running again.
Bill: If I had the money, I’d lend it to you. Why don’t you ask your brother? He’s loaded!
Adam: I don’t know that he can help me - his business has completely tanked because of the pandemic. He can’t even pay his employees.

FATHER: You look like you’re stuck - do you need help with your homework?
SON: I don’t know that you can help me with this - it’s Russian class.

Thank you! Then I'd translate it like
Вряд ли...
Отец: Похоже, у тебя затруднения. Тебе помочь с домашней работой?
Сын: Да вряд ли ты мне поможешь - это же русский.

ВРЯД ЛИ is too direct - in the English version, the speaker’s not sure. For instance, the son isn’t sure if his father knows any Russian or if he knows any Russians that could help him. In the other scenario, Bill hasn’t asked his brother, so he’s not certain that he can’t help him - he’s just assuming.

The best translation is я не знаю, не уверен

Адам: Не знаю, что делать. Я не работаю, как начался карантин, и машина как раз сломалась. Нужно начинать работу со следующей недели, а за ремонт мастер просит 500 долларов.
Билл: Если бы у меня были деньги, я б тебе одолжил. А почему ты не хочешь попросить брата? Он же при деньгах.
Адам: Да вряд ли он мне сможет помочь - бизнес у него встал из-за пандемии. Ему даже нечем заплатить работникам.

А-а, понятно 👍

And you couldn’t say “Да я не знаю, сможет он мне помочь или нет...”?

With вряд ли, the speaker is already answering his own question and say “no he can’t help me.” In the English version, the speaker hasn’t asked and doesn’t know, but is considering what he DOES know about his brother’s situation.

Да, так!
Да я не знаю, сможет ли он мне помочь.

👍🏼

So we’re back to the original Russian post)))

At the same time, if he DOES know about his brother's situation he almost knows the answer... that's why I think вряд ли is also good...

To me, it sounds a bit too direct, but when it comes to Russian, you know best. I would translate that as “I doubt (very much) that he’ll be able to help me” which is not what “I don’t know that” means.

It just means “I don’t know” not assuming anything else))

But if he really didn't know that his brother could help him, why didn't he ask him then???

OK!

He hasn’t asked him YET - he’s just weighing some of the factors before he does. This just expresses that moment when you’re like “should I ask, should I not ask...”

👍

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🌝