Let's look at the vowel sounds one sound at a time. The best way to re-train your brain to hear these sounds is to use listening skills. But being familiar with the variations in spelling will also help you succeed.
The sound /i/; or "vowel ee," is common in most languages, so we will begin with it. In English, this vowel sound has at least nine different ways that it is spelled, and likely more. You can see examples of the sound's various spellings in the chart below. To learn more about pronouncing this sound, you can read here.