This Scientific Research paper is a procedure of an automated system "Doly: Bengali Chatbot" which gives a reply to a user query on behalf of a human for the education system in the Bengali language. This is an AI-based Chatbot, mainly based on machine learning algorithms and Bengali Natural Language Processing (BNLP). The machine gets embedded with this knowledge to identify the desired sentences and making a decision within itself, as a response to answer questions. There are many English Chatbot's which used in education, web query, banking sector & various sectors. In this research, we have propounded a complete data-driven retrieval based closed domain Chatbot which is easily colloquy in the Bengali language with the users. We've created the train function adapter to train the Doly by encoding (encoding="utf8") our corpus from bot data. An input adapter has been created to take input and for output, an output adapter has been created to generate automated responses to a user's input. We have also used a machine learning algorithm like search algorithm for finding an appropriate list of matching results from the corpus and use Naïve Bayesian algorithm to generate the right answer from data. The main aim of this Chatbot based system is to bridge the gap between the knowledge sources by providing instant replies to the questions and queries that have to ask in the Bengali language.