Flat intonation is not the real problem

Korean speakers obsess over sounding natural and fixing pitch, but a native speaker will forgive flat intonation much faster than they will forgive a missing article or a dropped plural -s. If you stress every word equally, they still understand you. If you say "I need information about course" instead of "the course," the grammar error signals that you have not mastered basic structure. Band 8 writing requires article accuracy, not prosody. Fix the skeleton first, then worry about the melody.