A bolt from the blue ( সম্পূর্ন অপ্রত্যাশিত ) The news of his father's death came to him as a bolt from the blue.
At home ( দক্ষ ) He is at home in mathematics.
Rank and file ( সাধারণ লোক ) We should pay attention to the rank and file of the country.
A blessing in disguise ( বিপরীতে হিত ; প্রথমে খারাপ হিসেবে মনে হলেও পরবর্তীতে ভালো হয় ) Sam's motorcycle accident was a blessing in disguise because he got enough insurance money.
Build castles in the air ( আকাশ কুসুম চিন্তা করা ) Don't idle away your time in building castles in the air.
In a nut shell ( খুব সংক্ষেপে ) Tell the story in a nut shell.