In the previous question, the correct translation of "This is the main question" was given as "Ini pertanyaan yang utama". So on this one I answered "Ini gedung yang utama", but it was not accepted. Why?
Both "Gedung Utama" and "Gedung Yang Utama" have the same meaning. But, the first is more effective.
At least, "Gedung Yang Utama" should be accepted. We can report it.
"Ini ada gedung utama", was not accepted. Would this be considered correct?
In Indonesian, people say "Ini gedung utama" or "Ini adalah gedung utama".
Your sentence: "Ini ada gedung utama" is almost right :)) and seems to be influenced by Javanese language. I mean: Javanese and not Japanese.