good job, they are all right, but they will have different meaning in different contexts

I understand the word "before". This question has nothing to do with "before". Let me say in this way. " They rushed in and took a horrified look at the scene." What I meant is, before you looked at the scene, how could you know you would be horrified? But this expression, "took a horrified look" sounds like that looking and feeling horrified at the same time which I think is impossible.

I think the first sentence should introduce yourself. As a Chinese, if I write a letter like this, what I want to know first is the information about the writer. And it also shows your respect to the people who will read the letter. You can make your audience feel more intimate by introducing yourself, and gain the interest.

金腰燕在桥下开始筑巢。

金腰燕从南亚洲来到这儿了。它的躯体和一般的燕子<strike>的</strike>不一样，<strike>稍微橙黄的</strike> 是微微的橙黄色。它们在桥下开始筑巢。

hehe your Chinese is good. Practice is the only way to speak good Chinese. Just use it more often!