JE NE PEUX PAS OUVRIR MES ARCHIVES
I'm afraid that without more detailed information about the circumstances, nobody can help you.
Possible problems & solutions:
1.) Some archive types (e.g. ACE) are generally not supported by 7-Zip. Use another archiver that supports it instead of 7-Zip.
2.) The archive type *is* supported, but some archivers use methods that 7-Zip doesn't know or they simply don't follow the specification of that archive format. It's difficult to tell which other archivers are able to handle a non-standard archive but of course the archiver that was used to create the archive should work.
3.) The archive is broken. Get the archive again and see if it works. Some archivers, like WinRAR, let you repair the archive to some degree, but that depends on the archive type.