一問高手..

Things went wrong from the beginning. 口語化即係「一開始就有唔妥」, 因為無下文睇唔到呢句想實際想表達啲乜, 估計係無野生火或者個 camp 响海灘入水諸如此類

Things 係 plural 眾數, 因為未指明是「那些東西或事情」, 所以咪唔用 article 囉

People are blind.
Those people are blind who rush for the stock sale.
The people are blind when they rush for the stock sale.

Things went wrong from the beginning 文法上沒有錯。因為你所指的things是個collective term（泛稱），所以要用眾數而沒有article的。

段落的問題是你一開啟便說有問題，但由始至終你都沒有提及你的所遇到的問題。句子的意思也比較鬆散，例如你可以用一句話去說完了首三句的內容：
A few weeks ago, I went camping with my classmates on a beach in Sai Kung.

如你要寫Things went wrong from the beginning，你要清楚介定甚麼時候是beginning。是你們還未出門的時候？你們到達西貢的時候？在海灘露營的時候？

如果你想你的英文有所攺進，在你作文時最好是先用中文寫一遍， 然後才用英文寫出來， 就像你這篇文， 你試試用中文翻譯出來自己看看．

數星期前，我繼續(went on 是 go on 的過去式)一個露營，在那裡（還是在何處? where 之前應該是地點或地方名稱, I visited Tokyo WHERE I had bought a PS3 for my younger brother), 我和我的班級露營，你可以和你的班級露營而不是同班同學嗎? You should write: We camped instead of I was camping..........你也不可以用過去進行式，除非你在說當時你在做那些事還在做什麼其他事，e.g. We went to fishing when we were camping...........還有還有，但不寫了，你先用中文寫一遍吧，會對你的寫作會有幫助的．作文時最好是要合理，如果不是真的everything went wrong, 就不要亂說 everything went wrong，　若你真的想說 everything went wrong, 你便要指出一些 wrong things，和跟你所想講的有關連．否則便變了東拉西扯，只是為了填滿字數．

No need article before "things" here.
The rest is correct.

Few Days Ago, I went a camping trip . I was camped with my classmates. The trip was at Sai Kung and near at the beach.

The sentences i make it , , hope you will agree this sentences ^^