Corrections in red.  Stylistics in blue.

Correct my text please.

Imagine that a man and a woman share a twenty steps. Therefore, the [1] woman should take her ten steps, and stop.  If he does not meet you there, do not take the eleventh.  If you do, you will then have to take the twelfth, thirteenth, and so on, all your life. Everyone needs to take his or her ten steps!

[1]  We use the definite article because we have a specific woman in mind.  Which one?  The one that we are imagining, as you requested us to do in the first sentence.

"make" a step is not wrong; but "take" a step is much, much more comon.  To me, "take" sounds more natural, but obviously those people who use "make" might disagree.

Correct my text please.

Imagine that a man and a woman share a twenty steps. So, a woman should make her ten steps and stop. If he did not meet you there, do not do the eleventh - and then you have to make the twelfth, thirteenth, and so all my life. Everyone needs to make their own ten steps!