~T. Jenna
First I think i can be good at personal assistant because I like to support someone and I've done a lot.
>>First, I think I can be good at being a personal assistant because I like/enjoy supporting others and have had a lot of experience doing so.
I did in the club, such as accounting, making promotional posts and schedule management.
>>I gained experience in the club with tasks such as accounting, creating promotional posts, and managing schedules.
Second I can be good at social worker.
>> Second, I can be a good social worker.
OR
>> Secondly, I believe I could be effective as a social worker.
I've been doing volunteer work for almost two years, and I feel very rewarded for helping people.
>>Ive been doing volunteer work for almost two years, and I feel very rewarded by helping people.
OR
>>I have been engaged in volunteer work for nearly two years, and I derive substantial fulfillment from assisting individuals.
Especially I am interested in welfare system and people's mind too.
>>Especially, I am interested in welfare system and people's mind too.
OR
>>I am particularly passionate about both the welfare system and understanding people's mindsets.
Third I can be good at quality control.
>>Third, I can be good at quality control.
OR
>>Thirdly, I believe I would excel in quality control.
Because of majoring in chemistry, I did a lot of experiments.
>>Because I majored in chemistry, I did / conducted many experiments.
Quality control is not about making new things like research and development, but about repeating experiments.
Correct, or
>>Quality control is not about creating new innovations, as in research and development, but rather about repeating and verifying experiments.
I think repeated experiments would fit better than making something new.