Phonological differences

English and Russian differ in phonological systems. These are transformational rules that cause one phoneme to change into a particular allophone in a particular phonetic environment. Since we are often unaware of our both own language's phonological system and that of our target language, and because sometimes these rules are complex, this challenge will be one of the most difficult for you to overcome. But if you do, you will be well on your way to sounding native.