to travel in a group or by one self
People seldom agree with each other on such subjective questions that we hardly find the best answer to convince both sides. As we see, although in my country, most of travelers prefer traveling in a group, and I believe it is the so-called "DIY trip" is suitable for me.
Freedom is very important. If you join a group, you have to obey the leader of the group, a guide or someone. That means working instead of entertaining! I still remember the unforgettable experience that I visited Singapore all by myself last year though I wasn't an adult then. I got up till noon every day, and then read the guide book while enjoying my coffee which was provided by the hostel. What’s more, I can start my schedule whenever I want, and go to the place whichever I am interested in. To tell the truth, what I really want to see (delete “for”) most are not grand buildings or famous spots, but the view that can reflect the local life. Just like my vacation in Singapore, what impresses me most is the day that I spent in Changee village.
On the other hand, to travel by my own can be a good "social lesson" which has taught me how to communicate with others even we don't have a common language to use , and how to cope with some emergency such as an injury in such a remote country. The most notable challenge was how to be independent. After I had conquered this, as for me, I felt I really learned a lot when I was in the trip.
Nevertheless, I am not saying that there is no advantage in traveling in a group. As a good saying goes, existence is rational. The strong points of traveling with others are undeniable for e.g. it isn’t necessary for one to think about where to live and visit, and even what to eat in an unfamiliar country. Doing so offers you a chance to make more new friends as well. But for me, a guy with the mind full of spirit of challenge, to travel myself is always the best option.

总体来说没有什么致命的语法错误，词汇运用丰富，句式结构比较完整，逻辑比较清晰，但是有些用词方面还有欠缺不足，同时稍加留意你的语言表达有些中国化英语。建议考试时不宜运用太复杂的从句结构，避免批卷老师因误解而导致误判成语法错误。此外文章最好用些过渡词来清晰文章的结构层次，比如at first /besides/furthermore/finally/in the aggregate/in my view/as far as I am concerned等。
以下是我对您文章中的个别错误进行的点评和我个人的观点，仅供参考！
(1)though I wasn't an adult then此句太中国式英语了，我建议可以这么表达：though I was not young enough/though I was too young/though I was so childish.

(2)and then read the guide book while enjoying my coffee which was provided by the hostel此句中的hotel你写错了，大概是笔误吧！不过要注意哦！另外这后半句的定语从句我觉得把which改成that更好些！

（3）What’s more,首先这个词在表意上非常正确，只不过太过口语化了，注意托福的笔试尽量用书面语，比如说Besides/furthermore.

(4)I can start my schedule whenever I want, and go to the place whichever I am interested in此句中start用的不是太好，因为schedule这个词有固定搭配的，应该用make,即make a schedule,至于这里的whenever I want事实上用一个副词就可以诠释了，比如freely/without restriction/unstrictedly/at random.我建议该句可以改成：I will be able to make a schedule freely and go to any place I want.

(5)To tell the truth, what I really want to see (delete “for”) most are not grand buildings or famous spots, but the view that can reflect the local life.首先To tell the truth不太native，可以这么表达Generally speaking/In general/In fact/Virtually.另外这里有一处语法错误，即most应该改为mostly.grand可以改为magnificent更好些，famous spots可以改为historical sites更好些，我认为but the view that 可以改为which做定语从句更好些！即我建议这句话可以这么说：Virtually，what I really want to see mostly are either magnificent buildings or historical sites, which can reflect local culture.

(6)Just like my vacation in Singapore, what impresses me most is the day that I spent in Changee village.注意 what引导的从句只能是表语从句或者是主语从句，不能是定语从句，所以what要改为which,此外most要改为mostly，the day改为one day 更好些。

（7）to travel by my own can be a good "social lesson" which has taught me how to communicate with others even we don't have a common language to use , and how to cope with some emergency such as an injury in such a remote country. 我建议can可以改为could因为can的语气比could要强烈，对于这种两选一的观点作文，没有一个绝对的正确与否，所以语气表达得更婉转些比较好！social lesson表达得不是很正确，有点Chinguish如果要表达社会经验，可以用social experience 或者直接用lesson即可！lesson本身就表示从社会经历或小事中汲取的经验与教训！注意have a common language to use 这里的to use 是多余的，因为have词义丰富，它本身就可以解释use.虽然cope with 与deal with词义相同，但它们用法不同，cope with用于一件很复杂的事，通常是工程项目，学术研究。而deal with用于处理琐碎之事，小事，突如其来的事。我认为托福讲究用词准确，所以我建议在这个词的用法上需要斟酌一下。我建议此句可以改为：to travel by my own could be a good lesson which has taught me how to exchange with others even if we don't have a common language, and how to deal with something emergent such as an injury in such a remote country.

(8)After I had conquered this, as for me, I felt I really learned a lot when I was in the trip. 我认为in the trip表意不够确切应该改为during the trip

(9)Nevertheless, I am not saying that there is no advantage in traveling in a group.这里的I am not saying that太过于中国式英语了，应该改为there is no denying that.这里可以改为：Nevertheless, there's no denying that there exists some advantages of traveling in a group.

(10)for e.g. it isn’t necessary for 写法上的错误，要么全部简写要么要写完整，for eg是错误的应该改为for example / e.g./for instance.这句话可以这么说：for instance, it's unnecessary for

(11)Doing so offers you a chance to make more new friends as well. But for me, a guy with the mind full of spirit of challenge, to travel myself is always the best option.这里的 doing so 改成what I do,option虽然有选择的意思，但是这里还是用choice比较好，你可以查阅下字典看下 choice,alternative,option这三个词的区别，特别是语境上的区别，选修课叫optional courses 表示一般两选一或多选一的选择用alternative 或 choice 更加好些！我建议这句可以这么讲，what I do provides me a chance to make much more friends as well,
But for me, a guy with the mind full of spirit of challenge. Therefore, I believe that to travel by myself is considered as a best choice.