I modified my local files (lots of important things)
I tried to commit, but there were some conflicts
I just updated (download distant files) and resolved conflicts (hoping it would replace "distant" files by my local files/working copy).
It didn't do what I expected.
How can I revert my files as they were after point 1.?
Unfortunately that's not possible assuming you marked the conflicts as resolved. Once that happens, the three versions of the conflicted file (yours, the repositories, and their common ancestor) are merged into one (the resolved version that you said resolves the conflict) and removed from your working copy.
It sounds like you misunderstood what resolving a conflict is supposed to do. Conflict resolution does not modify anything on the repository; it's purely a local (on your machine) operation.