are these sentences correct? Or is there a better way to say any of these sentences?

Suzan didn’t know that her kidneys were going to fail at a young age. Had she have known, then maybe her eating habits would have been different. Then maybe she would have stopped consuming much of her diet with fast foods.

If Suzan had known ...

Finish that, but keep the ideas the same. One sentence should do it!
I'll check your work.

If Suzan had known, then maybe her eating habits would have been different; then maybe she would have stopped consuming much of her diet with fast foods.

Almost! Good try ...

If Suzan had known her kidneys were going to fail, then maybe her eating habits would not have included so much fast food.

(Or you could say, "... then maybe her diet would not have ... ")

Your sentence sounds so much better! Thanks Writeacher!

You're very welcome!

The sentences you provided are correct, but there are a few ways to improve the clarity and structure. Here's an alternative way to convey the same information:

"Suzan was unaware that her kidneys would fail at a young age. If she had known, her eating habits might have been different, potentially leading her to reduce her consumption of fast foods."

In this revision, I removed the contraction "didn't" and used the phrase "was unaware" instead. I also simplified the conditional statement by starting with "If she had known." Finally, I rephrased the last sentence to emphasize that her altered eating habits could have resulted in reduced consumption of fast foods.