What are the problems with my sentences?
You are asking 11 questions in one post. If I answer all of them, It will be a very long post. Therefore, I would only answer the first question here and please post other questions in individual posts.
&quot;是&quot; is the verb  &quot;is&quot;
One of the functions of &quot;的&quot; is as an possessive marker, adding it after a noun to indicate possessive.
Example: 中国 = China; 中国的 = &quot;China's&quot; or &quot;of China&quot;
Another function of &quot;的&quot; is as an adjective marker. Adding it after any phrase turn it into an adjective phrase
Example:  &quot;从美国来&quot; = &quot;came from America&quot; ;  从美国来的姑娘 = the girl who came from America

&quot;她是一个从美国来的姑娘来中国训练中国的足球队。&quot; is a run-on sentence
&quot;她是一个从美国来的姑娘, 来中国训练中国的足球队&quot;。(&quot;She is the girl who came from America, came to China to train China's football teams&quot;) is the proper form.

&quot;她(是)一个从美国来(的)姑娘&quot; is  a correct answer for the adjective marker function. But your answer didn't use [是 + noun + 的] as a [verb + noun + possessive marker] form. If it was the requirement that you must use this function, your answer would be wrong.
The correct answer should be &quot;这(是)中国(的)足球队&quot; = &quot;This (is) China('s) football team&quot;