Nice work, and still have some things to improve. 1. 那个骑自行车的男孩看到了一只猫在爬树。（”那个“ == the，“一只猫在爬树” emphasize the action, your translation "一只在爬树的猫" is also Ok, it emphasize the cat） 2.You can omit the "的" between “重要” and “公路”, because usually we don't use "的" more than once before a noun to describe it。 3.他们第一次看到一部彩色电影时，他们还以为它是真的。（”部“ instead of “个”， it matches with movie, in Chinese “a” can be translated into different word depending the noun. “色电影” may let people misunderstand you meaning to blue movie or porn movie, so add "彩" to make it clear. 4. You missed a sentence. 5.那些荧光笔很次。（You can omit “像” and “次” to make it smooth，“次品” is noun，”次“ is adjective）

Yeah, they are right, I just made some modifications to make them be better. 2。 66号公路以前是一条从芝加哥到洛杉矶的重要公路。(killed the 的between 重要 and 公路) 3。 第一次他们看到一个彩色电影，他们其实觉得是真的。（彩色电影 is right，if you said 色电影, it will lead Chinese to think it is blue movie) 4。很多人进入过那片森林然后再也没有出来。（you forgot this sentence)

For me, I think the second sentence has a better translation. The word major can't directly be translated into “重要” in Chinese, it should be "主要“. So I　would say 66 号公路以前是通往芝加哥到洛杉矶的主要公路。