If this sentence said "a long, pretty spring" would the arabic be
ربیع جمیل طویل
"a long, pretty spring" will be:
ربيعٌ جميلٌ طويلٌ.
I guess so, yes.
It's not a sentence because it hasn't got a verb; it's a noun phrase.
Sounds like it should be feminine, but it's not.