您好，我是名留学生。下面我给你纯手动翻译下您的中文：
1我的优势是坚定的信念和执着的态度。
Always being determined and having a clinging attitude towards ambition are my unique advantages on others.
2、如通过面试，我能否保证7月15日至9月15日期间有充裕的时间并能准时参加相关体检、培训、大会筹备、组织等活动内容；
In the event of successfully getting through the interview, can you guarantee me abundant time for the health test, training, organising the meeting and other events during the period between 15th July and 15th September
3、如我成为替补志愿者，我能保证毫无怨言地无条件服从安排，并坦然接受这一结果；
In the event of my being a substitute volunteer, I could guarantee to obey all your arrangement in no questions, and frankly accept the announcement.
4、如顺利当选为志愿者，能否保证毫无怨言地无条件服从岗位安排，并保持工作热情；
If I am succeeding in being the volunteer, I promise to have no problem whatsoever to bear my responsibilities that assigned to me, and continue to remain my passion.
5、如顺利当选为志愿者，拿到工作补贴，打算给妈妈买双新鞋，报答她的养育之恩。
If I am succeeding in being the volunteer, I am going to buy a new pair of shoes for my mother after the first payment made by my employer, as a payback for her kindness and favour of nursing me.
问题补充：还有 金融专业大三的学生 怎么说？
University student in BSc Finance, Junior (这个是美国用)，英国可以用：year 3或者Final year
“专业证书”地道点怎么翻译？
speciality qualification
certificate也可以，不过certificate有很多情况是特指你拿到的那张纸！就是证书纸，儿不是抽象意义上的证书。
不要机器翻译。
100%纯手动。英国留学生。
祝：学习进步，志愿者工作申请顺利！