This is for a cover letter. Please help!
"I speak Spanish; I have a working familiarity with French and I am currently teaching myself Arabic."
I would itemize it as a list, sorted by level of familiarity (descending).
I am fluent in Spanish, I have a working knowledge of French, and I am currently teaching myself Arabic
In your original sentence, there are three distinct clauses:
It is awkward to join the last two with a conjunction, then use a semi-colon to tack that conjoined sentence onto the first one. Strictly speaking it is grammatically correct, but it is inconsistent and awkward.
Definition of semicolon: A punctuation mark indicating a pause, typically between two main clauses, that is more pronounced than that indicated by a comma.
There's nothing incorrect about the semicolon in your example, although a period may 'appear' better.
"I speak Spanish. I have a working familiarity with French and (I) am currently teaching myself Arabic."
Note: My recommendation splits the sentence based on two aspects: 1. Fluency in Spanish. 2. Familiarity and efforts to learn another.