Hi! Are these ok? Thanks, Fulvio
1. I wish I knew all the things I know now when I was younger.
2. I wish I knew all the things I know now.
You are wishing fora lost opportunity in the past; so, you should use 'past perfect': I wish I had known all the things (that) I know now when I was younger. I wish I had known all the things (that) I know now.
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You are wishing fora lost opportunity in the past; so, you should use 'past perfect':
I wish I had known all the things (that) I know now when I was younger.
I wish I had known all the things (that) I know now.
Yes, they are both fine.
I'd particullary rather leave "the" out: I wish I knew all things I know now when I was younger.