"I am working at the library since January."

Translation: Eu estou trabalhando na biblioteca desde janeiro.

[vivalahumanidad]

Is this the correct use of the continuous tense here or would another version be more appropriate in Portuguese?

[Paulenrique]

In Portuguese it works quite well, but in English the "present perfect (continuous)" works better....

[MattCunnin7]

Right. The original English is awkward at best. It would be better to say: "I have been working at the library since January."

[Paulenrique]

For sure your suggestion works better in English =)

[LotSparham]

The English practice sentence is grammatically incorrect. My suggestion would be that DL replace it with MattCunnin7's suggestion.

[vsandl]

The English is grammatically incorrect. If you use "since" then you must use a past tense. "I have worked here since..." or "I have been working here since...".