I’m not a native English speaker so perhaps my opinion is irrelevant. I think Yinna sounds fine, the way I would pronounce it, but as Jerry said, it’s NOT an English name. If you use a name that people haven’t hear before, you can’t expect them to know how to pronounce it. So either you must tell them how to pronounce it or you must choose a name they already know how to pronounce. To me Yinna seems pretty straightforward. I would pronounce it as /jɪnə/ using the IPA (international phonetic alphabet).

Yinna is not even close to being a name in the English language. It's just something that you invented, as you said.

As a native speaker of Korean, this name sounds like a Korean name to me.

'Sarah' MUCH better!