With an activity, this is how it's worded in German. Eg: "ich laufe gern, ich spiele gern ( Ilike walking, I like playing ). One uses moegen more when referring to nouns or pronouns. Eg. "ich mag mein Auto, ich mag den Apfel ( I like my car, I like the apple ) Or "ich mag dich" (I like you.).
Both are correct. Pick whichever one you like.
It's a little bit like "till" and "until" in English -- there's no difference in meaning, and it doesn't really make a difference which one you use. So you might use one in one sentence and the other one in a different sentence. It's all good.
There isn't really one because there's no word in English that acts quite like gern.
(Some materials use "gladly" but I think that's misleading.)
The best translation is "I like swimming" or "I like to swim".
Basically, treat gern + verb as "like VERBing" or "like to VERB".
I just saw it translated as "willingly" in Wiktionary, which at least helps me understand the structure of the sentences. It's not a verb! OK, so it's not quite like "mögen" either (as in "to wish sth") but it's a German equivalent for similar cases in real time scenarios. Noted!
The verb has to be in the second position. If you put the subject first (the neutral word order) then the verb must come next; so there's only one place left for gern in this three-word sentence.
The default place of an adverb is right after the (conjugated) verb, unless there's a personal pronoun after the verb.
Duo uses "gern" as another way of saying "like to." As I use it with German speakers and have looked up, it also means "gladly" or "with pleasure." Duo has had complained when I translate "I like to..." as "Ich mag ...). Both are correct as in English we'd say "I swim gladly" or "I like to swim."
Usually doesn't convey the meaning of the German word well.
Sometimes, gerne has that meaning, e.g. Ich helfe dir gerne! "I will gladly help you!"
Or something close: Ich habe dir gern geholfen! "I was happy to help you! I'm happy to have been able to help you!"
But more often, it's better translated as "like": Ich spiele gern Gitarre is "I like to play the guitar", and translating it as "I play the guitar gladly" would sound odd to me at best; I don't think it captures the meaning of the German sentence well.
It's a bit, perhaps, like "translating" the word "really" as "in reality".
"This dog is really big" does not mean "In reality, this dog is big (even though it's small in my imagination)".
This translation changes grammar. Ich schwimme gern = I like swimming. Gern is the adv, while in English "gern - like" becomes the verb ? If I translate to Romanian would be "Eu inot cu placere" where things keep same role as in German Ich - Eu, schwimme - inot gern - placere. I mean "I like swimming" keeps the same meaning but the grammar changes.