BV is difficult for many linguest because it is a slip of the Lip on the upper front teeth. The B sound is the strongest sound of the two.There are many people who pull in both lips to hard and have to learn by seeing the sound spoken. In Spanish not all vowels are short,the stress sound is on the first vowel. I feel the situation here is if we were face to face we would have a better understanding of our conversation. These are really simple things complicated.