Intonation
Many people from different countries have improper intonation because their teacher had improper intonation. In many situations, being monotone is better than having bad intonation. The worst is when someone goes up and down too much on every word. Another thing you should avoid is to end high at the end of a sentence.
To correct improper intonation, you need to remember to start high and end low. You cannot do it any other way. I recommend going to the interview section and listening to one of the audio files provided by a native speaker. You will hear proper intonation. After listening to the audio, record yourself and listen to it. Does it sound the same? If not, then find the areas that are dissimilar and make the necessary corrections.
This advice is very trivial, but intonation is relatively easy to correct. You can fix your intonation with only a little effort. If you have a friend who is a native English speaker, you can usually fix intonation in a couple of lessons. Recording yourself and listening to yourself might be tedious, but having correct intonation can go a long way.
I have had many students who fixed their intonation after 2 small sessions. The advice I gave them was the same as the one above. This will work, and if you want to speak with proper intonation, please follow this advice.
Speed of speaking
A common mistake of people who obtain English fluency with improper pronunciation and intonation is the speed in which they speak. Because they do not have perfect pronunciation and intonation, it is difficult to understand people who speak too fast. This is the biggest problem I have seen from people who gain confidence in speaking.
In order to improve your communication, and to hear "excuse me" less often, it is important to have the correct speed of speaking. For people with confidence, my advice is to slow down and to speak clearly. Don't blend words together too much and make sure to separate words with a small pause for words that are difficult to pronounce.
参考译文：
语调许多来自不同国家的人语调不正确是因为他们的老师语调不正确。在很多情况下，单调比语调糟糕要好。最糟糕的情况是，一个人在每个字上都反复无常。另一件你应该避免的事情是在句末用高结尾。要纠正不正确的语调，你需要记住从高开始，低结束。你不能用其他方法做这件事。我建议你去面试部分，听一听一位母语人士提供的音频文件。你会听到正确的语调。听完音频后，自己录下来再听。听起来一样吗?如果不是，那么找出不同的地方，并做出必要的修正。这个建议很琐碎，但是语调比较容易改正。你只需稍加努力就可以调整你的语调。如果你有一个以英语为母语的朋友，你通常可以通过几堂课来确定语调。录下自己的声音听自己的声音可能会很乏味，但拥有正确的语调会大有帮助。我有很多学生在两个小课之后就把语调固定了。我给他们的建议和上面的一样。这将会起作用，如果你想用合适的语调说话，请遵循这个建议。说话的速度那些通过不正确的发音和语调获得流利英语的人经常犯的一个错误是他们说话的速度。因为他们没有完美的语音和语调，很难理解那些说得太快的人。这是我从那些在演讲中获得自信的人身上看到的最大问题。为了提高你的沟通能力，减少听到“对不起”的次数，掌握正确的语速是很重要的。对于自信的人，我的建议是放慢语速，把话说清楚。不要过多地把单词混在一起，对于发音困难的单词，分开时要稍作停顿。