My english course

Notes: The word 'didact' is extremely rarely used in English. This word has not been in regular use in English since before the 1950's. You can still use it, but I recommend saying "he is in fact a  good teacher, because he enjoys teaching others..." or "he is in fact a good teacher, because he is instructs us very well...", instead, etc. 

:)

My english course

I don't have to pay. The teacher is a good one, and has a master's degree, but I realized that he often fails in some things, like: He sometimes doesn't know the proper meaning of an idiom in English, or they he translates a Portuguese expression literally to English, and the expression has no meaning in English. Apart form that these particularities, he is in fact a good teacher, because he has a good teaching approach, and knows how to entertain the students. Now I've joined this platform in order to practice my writing skills.

When you just say, "I don't pay," it makes it sound like you are refusing to pay. But your point is that it is a free class. 

"The teacher is a good one." That's fine, but it is more natural and simpler to just say, "The teacher is good." 

Instead of "good didact,"  we might more naturally say, "a good teaching method" or "an effective teaching style."