You need an official translator to translate official documents.

You could simply say: I am currently studying XXXXXXX. The XXXXXXX stands for the course you are taking (e.g. math, politics, art, economics, English, etc.). I am not sure what you mean when you say you want to translate the certificate of the course. If you are really talking about the group of topics you are studying in order to get a certificate from your school, then you could say: I am currently studying a number of topics in order to get a {degree} [or] {certificate} in XXXXXXX. In this case, the XXXXXX stands for the field that the degree or certificate will be representing (e.g. Chemical Engineering, Music, Computer Sciences, Linguistics, etc.).