The most difficult thing for the English speakers to do during the period when they learn Mandarin would be master the tones in Chinese language. Since there are no tones in English language, it is difficult for them to articulate the four tones in Chinese clearly and correctly. Most of them will be attracted as long as them start to learn Mandarin because the monosyllabic words with different tones carry various meanings. However, the frustrating thing is that they often fail to pronounce clearly even when they have mastered large number of words.
As a result, some of the foreigners will use facial expressions or gestures to express the tones when they talk with Chinese people. However, most westerners learn Mandarin not for the purpose of giving a speech or debating but to master the expressions frequently used in daily life. It is confusing for those English speakers who study Mandarin in China why the change of tones would cause such differences in meanings. But the most important thing is that they can master as long as they use the proper methods to practice frequently.