In English we say
I like Coffee.
But I've never seen anyone saying
Ich gerne Coffee.
Why is this incorrect?
Google translator gives translation as above English version.
Here am just considering the meaning like for gerne.
"Gerne" is an adverb, not a verb like "like." (The second like is a verb, the first is a modifier.) Gerne in this context means something like "gladly," as an adverb.
A correct construction is, Ich trinke gerne Kaffee. Roughly, "I drink coffee gladly," which can be translated idiomatically as "I like coffee."
Or even, "Ich habe Kaffee gern." This is roughly I "have" coffee gladly, or I have a liking for coffee.
The verb "to like something" can be translated as »etwas mögen«:
I like coffee.
Ich mag Kaffee.
You will like this book. Read it!
Du wirst dieses Buch mögen. Lies es!
Why did you kill Rocky? I liked him!
Warum hast du Rocky getötet? Ich mochte ihn.
The German adverb is hard to translate 1:1 into German, because it uses to appear in constructions, that are built different in Englisch.
Möchten sie mehr Milch? Ich bringe Ihnen gerne welche.
Do you want more milk? I would be pleased to bring you some.
Nein, du musst ihn nicht zwingen das Klo zu putzen. Er macht das wirklich gerne.
No, you don't need to force him to clean the toilet. He really does it willingly.
Ich bin gerne mit Ihren Vorschlag einverstanden.
I am happy to agree with your proposal.