I study Chinese too, but I never connected Esperanto's "ni" and Chinese 你 (nǐ - singular you).
Most likely because of different tones, Esperanto's is a flat mid range (something like 5th tone but long) or sometimes the Chinese 4th tone, but on the other hand the Chinese one is deep falling and then rising (3rd tone).
Both sound completely different to me. Now I'm cursed too, from now on I'll see them similar. :DDD
That would be,
Vi helpas min grande, I believe. Note that:
Helpi becomes the verb instead of a noun, replacing esti.
Mi becomes the direct, rather than the indirect, object (and thereby converts to min).
Granda (great) changes to grande (greatly).
TL;DR: While it carries the same sense, it's a completely different sentence.