请英文好的朋友帮助检查一下以下英语写作有没有错误，谢谢

Question

These three studies make significant contributions to an important fact of leaders in large companies which is group-wide company or Multinational Corporation. They all make useful proposals to address the issue of what does it take to be a successful business leader and manager in the 21st century. It is recommended that further studies are important source of competitive advantage for companies.

Answer 1

第一句话：
1. these three studies改成the three studies就好了
2. make significant contributions to后面的内容不是很清晰。为什么做出了巨大贡献。仅仅说了an important fact是发现了一个fact呢，还是其他？不得而知。
3. leader我想这里你想要表达的是leadership，领导能力的意思。
4. companies后面不应该用定语从句，其实几个名词，用作同位语就好了

修改后是这样的：These three studies make significant contributions to the findings of an important factor of leadership large companies, especially group companies or multinational ones. .

第二句：
1. make useful proposals读起来怪怪的。好像没有useful proposal这个表达法，useful suggestions更好。
修改之后是这样的： They all make useful suggestions in addressing such issues as what makes a successful business leader or manager in the 21st century.

第三句：
1. compeitive advantage我才你是想表达竞争优势。其实competitiveness一个单词就够了。
2. recommend在这里好像不太合适。不是单词不对，而是你好像没推荐什么。
修改之后是这样：It is suggested that further studies are important source of competitiveness for companies.

Answer 2

These three studies make significant contributions to leaders in large companies of group-wide company or Multinational Corporation. They make useful proposals to address the issue of what does it take to be a successful business leader and manager in the 21st century. It is recommended that further studies are important source of competitive advantage for companies

Answer 3

They all make useful proposals to address the issue of what does it take to...建议改成They all make useful proposals to address the issue that it takes to

Answer 4

这么长的三个句子，让人看着很头晕，老外也不喜欢。你需要先把句子简化，然后再说语法问题。相信我说的，三个海外硕士，英文论文写了得有10万字了。