Adapt iPhone 8 to Wider iPhones

I'm having trouble making my iPhone app in the storyboard look the same on wider iPhones when I run it. I use a freeform style that is 375 by 1000.
Have you defined constraints ?

Anyway, it will not look exactly the same (unless to force the view size to the smallest one or embed in a scrollview (not very user friendly).
I defined constraints but when I increase the width of my freeform the lines get bigger and I lose one in my ui. How can I have a one size fits all?

 defined constraints but when I increase the width of my freeform

what is this freeform ?

the lines get bigger

which lines ?

and I lose one in my ui.

you lose one of what ?

How can I have a one size fits all?

that question does not really make sense. You want an UI that adapts to the screen, probably, not one size fits all.
Adapt iPhone 8 to Wider iPhones
 
 
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