How can I change my mile time from 9 minutes to 8 minutes?

How good is 9 minutes anyways? I actually felt like I wanted to go faster but I was afraid of falling and my knee kinda fell out twice. Not a big deal but still. Also I'm running on old sneakers that have seen thousands of miles. Anyways - How long till I can do an 8 min mile?
How can I change my mile time from 9 minutes to 8 minutes?
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