Well, no surprises here, no special difficulties - just a useful phrase!

Let's start with the "vague" word. "Vague" in Hebrew is מעורפל (MEURPAL).
An interesting fact may be that it comes from the word ערפל (ARAFEL) - which is "fog" or "mist" - like in "the valley is covered by fog" - העמק מכוסה בערפל. (audio #1)

Some examples of "vague"
⮞ The meaning of this article is rather vague. .המשמעות של המאמר הזה די מעורפלת (audio #2)
⮞ A dim childhood memory. .זכרון ילדות מעורפל (audio #3)

Now, how do we turn "vague" into "vaguely"? This may be interesting, actually! To turn this adjective into an adverb we just need to add BE- (or BI- in this case, to be exact) - במעורפל BI-MEURPAL.

Examples:
⮞ I remember something like that, but vaguely, without details. אני זוכרת משהו כזה במעורפל, אבל בלי פרטים... (audio #4)
⮞ I vaguely remember meeting him. אני זוכרת במעורפל שפגשתי אותו פעם. (audio #5)
⮞ I vaguely felt that it's not going to end well. הרגשתי במעורפל שזה לא הולך להיגמר טוב (audio #6)