3 primary weaknesses of public speaking

As a speaker, everyone has their own strengths and weaknesses in public speaking. For many people, having difficulty in researching the topics, identifying the audiences or conveying the message may be their main problems. But for me, finding the ideas, using the correct vocabulary and being more confident are three primary aspects of speechmaking that I most want to improve. Today, I am going to share with you about my major problems and how I can handle them.
The first problem I would like to talk about is that I really get stuck at finding the ideas for my speech. This is the most difficult part for me. For example, when I receive a topic about literary or chemistry, it will take me hours to find out the ideas. But in contrast, if the topics are about economy or science, a lot of ideas will come up to me for seconds. It is because my knowledge does not cover enough for the fields that I may not be interested in like literary, chemistry ... So, if I want to improve this weakness, all I have to do is balancing my knowledge. I need to read as hard as I can to cover up the knowledge of the fields that I missed so that I will have more ideas to talk about whenever I receive a topic, no matter it is my favorite topic or not.
The second issue I want to mention is that I am really bad at using the correct vocabulary for each topic. For instance, when I have already found out the ideas for my topic, I still have difficulty in choosing the right words to express my ideas. The reason is simply because I came from a different country where English is even not the second language. Once again, to solve this problem, I need to get accustomed with the language, with the culture here. I have to read as possible as I can because it is the fastest and only way for me to obtain enough vocabulary for public speaking.
The final problem that I meet when I do public speaking is lack of confidence. It may happen to many people, but for me, it makes me feel extremely hard to express my