The tour guide, Tuji, shows a lake

How do we tell if one is good at a language? Sometimes one is just doing literal translation on the fly, which is a fake kind of fluency.

Intended conversation:

Tuji: There was a beautiful lake here.
Tourist: How sad.

However when this conversation is conducted in another language which has ambiguity with past and present.

Modulo tense, we get:

Tuji: There is a beautiful lake here.
Tourist: Where? I don't see it.
Tuji: Wait what? Why do you expect to see the long-gone lake?

People say usually in this case, Tuji should put in some extra words to indicate the past rather than simply translating. They all have difficulty understanding Tuji. ;_;