The correct translation of “মানুষ কোথা থেকে হলো, সে যাবেই বা কোথায়?” would be

Where had man come from and where will he be going?

Where was man found, where will he enter?

Were is man coming from and where is he going?

Where is man's post, where is his future?

Where did man come from and where will he go?