Communication breakdowns can 100% occur even when you pronounce the words correctly. Many non-native English communicators expect it to be black and white; understood or not understood, native speaker or non-native speaker.
There are many reasons why miscommunications can occur.
Pitch and intonation play a huge role in conveying your message clearly.
Pitch and intonation refers to the range of your voice and its use in multi-word phrases.
When you ask a question, your pitch rises at the end of your sentence.
When you say a statement or fact, your pitch falls at the end of your sentence.
If you ask a question, “How are you?” but your pitch falls at the end, you are sending mixed signals.
If you are saying a statement, “Yes, I can do it?” but your pitch rises at the end, you are sounding uncertain.