How do you know whether the person is saying 'live' or 'leave'? From the context, and the grammatical construction of the sentence. There is never any cause for confusion with regard to meaning.
As for the phonology, they are actually totally different sounds, both to the native speaker ear in the native speaker's mouth.
'Live' is a slightly shorter sound, and it's made when the mouth is relaxed. There's no contact between any parts of your mouth when you say 'i'.
By contrast, your mouth is much tighter when you say 'ea' or 'ee'. The muscles are more tense, and you can feel the sides of your tongue pressing against the inner sides of your teeth when you say this sound.
If you want to practise the sounds yourself, first relax your mouth, so that no parts are touching, and say a short 'i' sound. Then say it again, but this time tighten the muscles of your mouth so that you can feel the pressure on the sides of your tongue, and say the consonant 'y'. The transition from 'i' to 'y' will make you say 'ee'.
Once you are able to pronounce the two sounds clearly, this will improve your perceptive skills and help you understand what you are hearing.