Your friend has likely made an error. The literal content is "brutal/harsh/brutally/harshly/harshen true/right/truly/rightly now/currently/presently/still". There is certainly no "I'm" there, which would be zu'u los or simply zu'u.

The "I'm" may be implied. I thought that when the subject of the sentence is omitted, it is assumed that the subject is the speaker.

Also, "Harshly true/correct now" is likely only NSFW in certain contexts. I'm familiar with some of the more NSFW translations of euphemisms, but "Hevno Vahzah Nu" sounds perfectly tame by itself.