why does tae saying yevgeny mean he getting it im lostt

Yevgeny is his full russian first name, Zhenya is a nickname/shirter version of Yevgeny.
In this context it could mean a very serious tone

'Zhenya' is like this (the last part) of the name Yev'geny', the Zh is pronounced like a version of the second G in the word 'garage' -> Genya