The English pronunciation of the letter V may be different from your language. Sometimes it doesn't matter - the listener may understand or may not notice the difference. But sometimes it DOES matter, especially when your listener is old, like me, or perhaps more importantly, when there are words that are similar in pronunciation:
So how should you pronounce the letter V in English? It's actually pretty easy!
The mouth formation for the letter V is very similar to how the mouth forms the letter F:
The bottom lip touches the tip of the upper teeth.
With the letter F, you blow air with some voiceless force. Say, "FINALLY!" like you are excited that a new movie opened. Put your hand in front of your mouth as you are saying it. Feel the air coming out strong? Maybe you spit a little. Maybe that's just me. It happens, ok?
With the letter V, you kind of vibrate, or blow softly, using your voice. Try saying, "Very vexing," (because that movie was confusing!) with your hand in front of your mouth. See how much softer it is? Although the lip made the same formation.
Now, try saying, "Five very fast vehicles swerved violently." See? Pretty easy, right? You sound great! Keep practicing. Your pronunciation will be clearer - for old folks like me!