I agree with Brett - all of these are spot on, but the last one could use some rewording. You can "take something for granted," or "take for granted the fact that + main clause." In this case, I think Brett's suggestion is more elegant and natural.

Thank you so much Brett:) it helps me a lot!

I think you've done remarkably well! Only the last sentence is difficult to follow, or "clunky". Perhaps something like: - John shouldn't take for granted the fact that Petra has been at his side supporting him all these years. It's a little lengthy, but elegant and precise. Good work!