For learning Bengali language it is necessary to know alphabets in Bengali. You have to know alphabets in Bengali to learn writing in Bengali language. Bengali alphabets are the building blocks of Bengali language. There are 51 characters in Bengali alphabets. Bengali alphabets are made up of Bengali vowels and Bengali consonants. The Bengali alphabets contain 11 vowels and 40 consonants. Bengali vs German gives a comparison between Bengali and German alphabets.
Bengali script is also known as Bengali writing system or Bengali orthography. The set of visible signs used to represent units of Bengali language in a systematic way is called Bengali Script. The Bengali language uses Bengali, Brahmic family and derivatives i.e. Bengali alphabets are derived from Bengali, Brahmic family and derivatives script. The script decides the writing direction of the any language, hence the writing direction of Bengali is Left-To-Right, Horizontal. Learn Bengali Greetings where you will find some interesting phrases.
Is Bengali hard to learn? The answer to this question is that it depends on one's native language. One should start learning Bengali language with Bengali alphabets and Bengali phonology.
Time taken to learn any language that is mentioned here is the approximate time required to learn specific language for the person who is proficient in English. You can also go through all Indian Languages and find if Bengali is one of the language of India.