I work and live in Belgium however I am Brazilian and I want to take a drivers license in a country that I can do the test in English. Can I take the driving license tests in the UK and then be allowed to drive in Belgium?
No. You can only apply for or renew a UK driving licence if you are resident in the UK. Furthermore, the DVLA requires proof of immigration status when you apply for a driving licence, if you are not from the UK/EEA/Switzerland. Since you won't have this, it is impossible for you to get a provisional licence.
I...live in Belgium.... Can I take the driving license tests in the UK...?
No. Like most jurisdictions, the UK grants driving licenses only to residents of the UK. This is such a fundamental assumption that the government's public information pages do not mention it explicitly, but if you start the process to apply for a provisional license, you will see that you cannot enter addresses outside the UK.