"genießen" is more used in connection with nouns. (You can compare that to "mögen" for "to like"). "Ich genieße mein Eis." = "I enjoy my ice cream." or "Er genießt seinen Urlaub." = "He enjoys his vacation."

Otherwise, as "genießen" like "mögen" does not grammatically work with verbs, you have to create a subclause to make it work. "Ich genieße es, zu lernen." would be the shortest version. (The "zu lernen" part is a grammatical construction that is not part of the mainclause, although the comma is not always needed.)

In this case I would prefer the longer translation with "genießen" over the translation above. "Ich lerne gern." is more "I like learning." Some aspects of enjoying are lost in translation.

I hope I could be of help.

PS: For the adverbial route: "mit Freude" would work. "Ich lerne mit Freude." is essentially the ame as "I enjoy learning."