Yes, this one again! I think that even if you mix up these two sounds [i:] and [I], the context makes your listener understand. In linguistics, the first of rule of communication is to cooperate. This means making an effort to understand and responding with an appropriate anwser.
For example, you might mispronounce the word ‘ship’ (bateau), making it sound more like ‘sheep’ (mouton). If your listener doesn’t follow this basic rule of cooperation the conversation would go like this:
So how was your holiday?
– great, we went on a cruise.
Really, what was it like?
– Wonderful, the ship [shi:p] was enormous, and there plenty of things to do.
What? You travelled on a woolly white farm animal?
Of course you wouldn’t say something like that, because the word ‘ship’ – whether it is pronounced correctly or not – is defined by the context: holiday, cruise, etc.
Any keep practising, it can only make you better….