I can't speak to the Hebrew, but in the English - I left my (exciting) life in another place and now I have no life (aka uneventful).
It's an expression in English "to have no life" = you don't do anything. It could be that you literally don't do anything, or that you only do bare minimum , work/sleep/eat but nothing interesting.
Hayah היה = he was, it was (ms)
Hayu היו = they were
Khaim חיים, which means life, is a plural noun, so it needs a plural verb.
Also, when you say "I had a life" in Hebrew, what you are literally saying is "There were life (plural) to me".
Here are some other words that are singular in English, but plural in Hebrew:
Shamayim שמיים = sky, heaven
Mayim מיים = water