just my two cents:
1/
However, after working for few weeks, I realized that it is "defining moment" of my career.
It is not very precise to use "moment" here, as it took you quite a while to change your mind.
I would rather say, after the first few hard weeks, strangely i gradually changed my mind.
2/
Besides work, I learned many words in Portuguese and got familiar to diverse African cultures. Furthermore, I interacted with colleagues from more than 20 different countries, enhanced my cultural tolerance and socially associated with them to build global relationships.
Suppose you may want to give some very special examples that makes you stand out more. Even though it is very interesting to be in far away countries, meeting the locals, learn a few new words or work with colleagues from 20 countries, I would say a lot of travelers or employees of multinational corp. may have the same experiences. Ad-com would expect to see something unique from that experience, imho.
For example, you can tell how you broke the language barriers to communicate with the locals...what your learned and how you changed your mind after that...
Or maybe you can tell about your teamwork or leadership experience in a multicultural environments...