In my view the main cause of these mistakes are less knowledge and information all about grammar rules

From my experience, the main problematic mistakes in this essay are related to grammar errors. There are a lot of mistakes connected to the tenses, the wrong use of the punctuation and spelling mistakes as well as wrong word-choice in some parts of the essay.

In my view the main cause of these mistakes are less knowledge and information all about grammar rules.

Simply, in order to improve your writing skills without grammar errors you should read at first all about it, know necessary rules and tenses , and glance many books about grammar.

My final feedback is try to work with well-educated teachers and take a lesson from them. And apart from that, make a habit to read books at least once in a week. Then you will the result.