Most English pronunciations involve the tongue and the roof of the mouth.
Chinese involves the tongue and the floor of the mouth.
The tongue is a muscle. Don't laugh, you have no idea how many Chinese do not know this. They have no idea that they need to retrain a muscle.
A great tool is provided by the University of Iowa.
Phonetics: The Sounds of English and Spanish - The University of Iowa
A great tool 
Linear Mode
