Hi guys i haven't seen any English guide for FOV that works online so i've made this.
Easy short guide how to have custom FOV.

Part 1 :
-Go to : "Documents\DyingLight\out\settings"
-And there you will see a file called "video.scr" screen saver file.
-Create a new Text document

◘◘◘◘◘◘◘◘◘◘◘If you don't know how to : ◘◘◘◘◘◘◘◘◘◘◘◘◘◘◘◘◘◘◘◘◘◘◘◘◘◘
-Right click at desktop or anywhere
-New ➡ Text Document
-And then just press "Enter" if you don't want to give a name to the text file
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Part 2 : Back to FOV changing
-Open : Documents\DyingLight\out\settings
-And Open "Next Text Document" too
-Hold Mouse 1 on "video.scr" and drag it into "New Text Document"
-Now you can see what's in it
-And there you need to find "ExtraGameFov (90.00)" (At "(90.00)" ⬅ There will be a different number like (15.00) , (52.00) or i don't know i don't remember what was the basic.)
-Now just change it what ever you want (i prefer using (90) )
- ( if you are done and wrote what FOV you want) Now in the "Text Document" go to "File" and there "Save As" and there before saving below the name of the "txt document " there is "Save as Type" and it will say "txt" but click to it and there choose "All files" and then click to save it to "Documents\DyingLight\out\settings" and it will ask you "do you want to replace it?" and click to "Yes"
-Now you are done just go launch Dying light and Have fun!
(Dying Light Basic fov + *The numbers that you wrote there* = incrasing FOV

******** You can't get VAC with this, and you can play online with anybody ***********

I hope i helped , and if yes please rate my guide ! ;) Have a nice day!