Hi Bruno, I'd recommend checking out belaws.com, they have an excellent team of legal experts who can help. Here is the link to getting a Visa and Work Permit for your situation
Sandee language school in RCA is your best bet. Its where I got my Ed Visa from a few years ago. I wanted to learn the language but it is a Visa mill, I stopped going after 3 classes as it was useless and got private lessons instead. Still got an extension. They dont care.