有几句英文,大家看看有语法错误没有啊,I have a boyfriend,we have been together for three years,and I love him very much.In high school,whenever I feel depressed,for grades sad,he is always very considerate to comfort me,and encourage me.Three years of time let us has experienced a lot.Perhaps some people don't think we will think we won't have the result.But we came over,and hope to keep going.

改正：
I have a boyfriend, we have been together for three years, and I love him very much. In high school, whenever I feel depressed for grades ，it is considerate of him to comfort and encourage me. During the three years，we have experienced a lot. Perhaps some people don't think we can continue，but we came over and now hope to keep going.

I have a boyfriend.we have been together for three years, and I love him very much.In high school, when I feel depressed because of bad grades,he will comfort me, and encourage me. Three years later,we have experienced a lot.Perhaps some people don't think we will have a good result,but we will continue.
is that ok ?

I have a boyfriend.We have been together for three years,and I love him very much.
（you need to use a period)
其他的.
We have been together for three years and I love him very much.(This sentence doesn't need a comma.)
In high school,whenever I feel depressed for grades sad (for grades sad?What is this?)
应该是：
In high school whenever I feel depressed about bad grades,he is always very considerate.He comforts and encourages me.（这样比较好）
这样比较好：
I have a boyfriend.We have been together for three years and I love him very much.
In high school whenever I feel depressed about bad grades he is always very considerate.
He comforts and encourages me.We have experienced a lot in three years.
Perhaps some people don't think we will make it,but we have come over many problems
and hope to keep going.

In high school, whenever I feel depressedfor grades, he is always very considerate to comfort and encourage me.
Three years's time have letting us experienced a lot.
Perhaps some people don't think we will think have a result.