As promised, here I leave you the presentation we saw in class to practise the pronunciation of these sounds.
Unfortunately, Spanish native speakers use both the sounds /b/ and /v/ for letters “b”and “v”. This makes that Spanish-speaking students of English have many problems making difference between these sounds. If you want to improve the pronunciation of these sounds you can check these video lessons taken from the BBC website.
If you want to practise the pronunciation of /b/, see this video.
If you want to practise the pronunciation of /v/, see this other video.
Finally, you can see this presentation again to practise these sounds in context.