I had a USA tourist visa in my Bangladeshi passport. But recently,I have taken German Passport. According to Germany rules, I can not use Bangladeshi passport. 1. What would be the condition of my USA visa that is entitled in Bangladeshi Passport???
Accourding to German rules, in general, you must give up your former citizenship before receiving German citizenship.
If you have given up your original citizenship, you may not claim to be of that citizenship. Any such claim would be considered fraud.
You must apply for an US ESTA entry as a German citizen. Upon application watch out if you are being asked about a former citizenship and possible former visas. Supply that information if asked or mayby, if supported, as a comment or remark.
Being upfront during your first application may spare you problems later.