Translation:I speak both English and Russian.
Sentences like this remind me of that moment in The Blues Brothers where John Belushi walks up to the barlady and asks what kind of music they do at Bob's Country Bunker, and she goes "We do both kinds: country AND western!"
Only there is a difference between English and Russian.
From the tips page for this unit:
“ To express the idea of speaking some language, or something being written in that language, Russian has adverbs literally meaning "Russian-ly", "English-ly" etc.. :
Я не говорю́ по-ру́сски. = I do not speak Russian.
Вы говори́те по-англи́йски. = Do you speak English?
They are formed from -ский adjectives by attaching по- and changing the tail to bare -ски: по-ру́сски, по-италья́нски, по-япо́нски, по-вьетна́мски, по-америка́нски, по-францу́зски and so on.
And remember, these words actually mean something done "in a certain way", so «суши по-американски» (American-style sushi) should not surprise you!”
That's quite a free translation, which is not necessarily helpful in a teaching context. One could argue that it's implied in the Russian, but я могу doesn't actually appear in the sentence. In this context, a slightly more literal translation is IMO more helpful to the learner.