i wanted to get back into modded minecraft but after installing forge 1.7.10 (because that's a version all my mods properly support) when i clicked play in the minecraft launcher it kept giving me an error about something but i'm not really sure how to fix it but it had something to do with a file which i checked out but i didn't temper with the file because i wouldhave probably made it worse so i just looked but everything seemed fine so i don't know what to do now so please help

 

(it's dutch hope that isn't a problem (i'll provide a self translated version just in case))

Error giving but censored without my personal info aka without user profile name:

Downloaden van het bestand is mislukt, omdat de bestandsinhoud anders is dan verwacht.
Naam: jopt-simple-4.5.jar
URL: https://libraries.minecraft.net/net/sf/jopt-simple/jopt-simple/4.5/jopt-simple-4.5.jar
Bestandsnaam op schijf: jopt-simple-4.5.jar
Pad: C:\Users\(my user profile was here)\AppData\Roaming\.minecraft\libraries\net\sf\jopt-simple\jopt-simple\4.5\jopt-simple-4.5.jar
Bestaat: File

 

The self translated version:

downloading file failed, because the file content is different than expected.
Name: jopt-simple-4.5.jar
URL: https://libraries.minecraft.net/net/sf/jopt-simple/jopt-simple/4.5/jopt-simple-4.5.jar
filename on disc(harddrive maybe idk): jopt-simple-4.5.jar
path: C:\Users\(mu user profile was here)\AppData\Roaming\.minecraft\libraries\net\sf\jopt-simple\jopt-simple\4.5\jopt-simple-4.5.jar
exists: File

 

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