Learn Farsi: آن جاسوس با دشمن رابطه‌ی دوستانه دارد. - That spy has a friendly relationship with the enemy.

It is made by adding the suffix -انه (-âne) to the noun دوست (dust, meaning friend). This suffix turns nouns into adjectives or adverbs of manner. Here, it acts as an adjective meaning "friendly" to describe the relationship.

Can the word دوستانه be used as an adverb too?

Yes! The -انه (-âne) suffix creates both adjectives and adverbs. In this sentence, it is an adjective describing a noun, but you can also use it to describe an action, such as behaving "in a friendly way" toward someone.

Why does رابطه (râbete) have a ی added to the end of it?

That is the ezâfe, which links the noun رابطه (relationship) to the adjective دوستانه (friendly). Because رابطه ends with a silent "heh" (making an "e" sound), the ezâfe is written with a ی to bridge the vowels, creating a "-ye" sound.

Why does با دشمن (with the enemy) come before the object of the sentence?

While Farsi generally follows Subject-Object-Verb order, prepositional phrases like با دشمن are flexible and are very often placed before the direct object. You could also put it after the object, but putting the prepositional phrase earlier sounds very natural.