I have recently completed the game and finished all the quests so to keep my self entertained i trying to install mods.
All the mods i try to install dont work even if i follow the exact steps.
I was recently trying to install a mod that needed to be placed in the patch0 folder and when i was trying to find the folder i realised that it was missing allong with all of my content folders except from content0

if the patch0 file is missing you cannot play the game, try launching the Witcher 3 see if it runs & is playable.
If the game works you are not missing the patch0 file now all you need to do is find it.

I have played the game cause i have more than 40 hours on it and my patch0 file is not where it is supposed to be .

yes & you have also tried to mod the game & by doing this altered the games files, since reading my post have you launched the game & is it playable?

you can check the games files to see if you are missing patch0 a couple of ways,
if you are using the Galaxy client select the game & use the "More" button move the cursor over "Manage" & select
"Show folder" this will take you to the Galaxy installation which should have all the files you need, then open the file called "content"

if you are not using the Galaxy client then use Windows Explorer & search for patch0, if the file is found right click on it & select "Open file location"

if you have tried to install mods & they are not working i suggest making backups of your save files & uninstalling/deleting all the Witcher 3 game files & then reinstalling the Witcher 3 so you have a completely vanilla game to work with.

The galaxy client has a "repair" button. FYI.

I have fixed it loads of time but still no patch0 file

in my post above i explain how to check if you have the file & i also ask you again, can you launch the game & is it playable?

Yes i can and it is playable

i am also missing the witcher.exe but i can launch and play it through gog galaxy i reinstalled the game and the files are no longer missing thank you

good glad you sorted it out.

The witcher3.exe isn't missing & you can find it by using the Galaxy client game menu options.

Click on the Witcher 3 in Galaxy
Use the "More" button then move the cursor over "Manage" & select "Show Folder"
A new window will open with all the Witcher 3 files in it, open the file called "bin"
Now you should see a file called "x64" open this file you will find the witcher3.exe