Slavs spoke the same language or similar dialects t1,500-2,000 years ago. Our languages began to diverge as Slavs got separated. Even all Slavs adopt the same artificial Slavic language it will get diverged again.
OCS is old Bulgarian being most similar to modern day Macedonian. I begin to think Slovenian is more of a west Slavic than south Slavic language despited being classified as south Slavic.
PS In Belarusian wolf is pronounced as in Slovenian voŭk or vowk. In Russian volk , in Ukrainian vovk.