Now I wish I had been there.
Şimdi burada olduğumu istiyorum.
"Now I want to have been there"
现在想想,真遗憾当时不在场。
Burada olmadığıma biraz üzülüyorum şimdi.
"Now my not having been there saddens me a little."
It's funny how the most natural way of translating counterfactual wishes from English into Chinese seems to be to turn them into regrets. Or maybe that tinge of regret was always lying just beneath the surface of "I wish I had"?
And then of course I have no idea about the idiomatic way of saying such things in Turkish. Both of those sentences might just sound downright strange to a native speaker ...