@imanis97_ Where are you deleting them from? It's possible, if you have your system set to sync with cloud storage (OneDrive or iCloud), you're merely deleting one copy, and the other is getting reuploaded or -downloaded afterwards.
Please list the full file path of the Mods folder where you keep deleting your mods. In Windows, you can see it in a File Explorer window, above the list of files. In macOS, right-click (or hold down crtl and click) on the Mods folder and select Get Info, then copy the information under Where. Either way, please paste the file path into a reply. You can write [username] instead of your actual username, but leave the rest of the file path intact.
Please also launch Sims 4, click Load Game, choose one of your saves, and hover over the folder icon underneath the save name and details. You'll see the file path of the save there; the Mods folder the game is reading will also be in the same Sims 4 folder. So if you're not deleting your mods from that folder, they won't actually be removed from the game.
I believe my mods folder is synced with Onedrive, how do I delete them from there?
Here's the location of the folder, C:\Users\username\OneDrive\Documents\Electronic Arts\The Sims 4
@imanis97_ There are a few different ways to delete the mods. The simplest, if it works, is just to delete the files on your hard drive and then in OneDrive immediately after, so no syncing happens. You know how to get into OneDrive's Documents folder already. If you're having trouble finding the Mods folder on your hard drive, open a File Explorer window, click This PC, then C, then Users\[your username]\Documents\Electronic Arts\The Sims 4.
If you get a message about a folder being in use, it's probably because OneDrive is syncing in real time. Copy the Sims 4 folder in the local version of Documents\Electronic Arts to your desktop, then disable OneDrive's auto syncing of Documents.
You should copy your Sims 4 folder to the desktop first because stopping the syncing may remove the contents of Documents from your hard drive and leave only a single copy in OneDrive. So you'll need to put the copy you made back in Documents\Electronic Arts before using it. If your original copy stays on your hard drive though, you can delete the copy. Either way, delete the mods you don't want, and you should be fine.
I deleted the mods on my hard drive and I opened the mods folder on onedrive but the deleted mods were already gone. Should I delete them from onedrive first? Would that permanently delete them?