The encryption oracle only allows you to encrypt a custom message $m$ or the secret message $m_s$. In both cases it asks you to choose a public exponent $e>16$. Of course, $n$, is not available.
If I had multiple queries, the first step should be to ask the oracle to encrypt two custom messages with the same exponent to compute $n$ with this GCD formula.
Then, I should ask the encrypted secret message twice $(c,c')$, with two different public exponents such that $gcd(e,e')=1$, then use the Extended GCD to get the $a,b$ coefficients.
The decrypted secret message would then be: $m_s=(c^a\mod n\cdot c'^b\mod n)\mod n$
By having only two queries, how is it possible to compute $n$ and decrypt the secret message?. Obviously, one of the two queries should be the encrypted secret message.