I'm sorry I already tried to find a solution by my own but failed. I tried to download the game again since I thought some files were corrupted, but it didn't work.
So I tried opening the game while my computer was starting up, like I usually wait a little while it sets up, but today I opened the game as soon as the computer logged in, and this error occured. I know some people experienced the same issue but I couldn't find a solution in the treads I found. I'm not very confortable trying to solve the problem by myself and I am afraid I might ruin my game in which I invested so many hours.
Thanks in advance, and sorry again to bother.