To take a leap in the dark -

• A leap in the dark:
- English Meaning: To do hazardous thing without any idea of the result/ something you do without being certain what will happen as a result.
- Bangla Meaning: ভবিষ্যৎ বিবেচনা করে কাজ না করা।
- Ex. Sentence: I had very little information about the company, so writing to them was a leap in the dark.

Source: Cambridge Dictionary