you think/do you think....

যেটা ভালো সেটাই করেন।= Do whatever is right.

আপনার যেটা ভালো মনে হয় সেটাই করেন।= Do whatever you think is right. = Do whatever you deem right.

কারণটা কী? = What is the reason?

কারণটা কী বলে আপনার মনে হয়?= What do you think is the reason?

কে এটা করেছে? = Who did this?

কে এটা করেছে বলে আপনার মনে হয়? = Who do you think did this?

সে কী করছে? = What is he doing?

সে কী করছে বলে তোমার মনে হয়?= What do you think he’s doing?

Do whatever is right. (Sounds very straightforward and kind of like an order, doesn’t sound very friendly)

Do whatever you think is right. = Do whatever you deem right. (This sounds more friendly and persuasive, doesn’t sound like an order)

More Examples:

What is the reason?

What do you think is the reason? = What according to you is the reason? = What in your opinion is the reason?

Who did this?

Who do you think did this?

What is he doing?

What do you think he’s doing?