Can somebody check out this for a grammar?

Hello everyone, my name is Togzhan. I’ve been a volunteer during the three months in the international organization which is called International Science and Technology center. My main duty was to introduce primary missions, activities, history, achievements of ISTC to the visitors of International Exhibition EXPO 2017. EXPO 2017 was held in the capital of Kazakhstan in Astana where our own country Kazakhstan and more than 95 countries, 22 international organizations including ISTC, were presenting their projects about possible ways of using renewable energy. Beside the projects in the field of future energy, many countries, especially Kazakhstan in order to attract visitors have showed their culture, traditional dishes, clothes, entertaining programs. Each country had had an own pavilion and international organizations are not exception. 22 international organizations such as UN, OPEC, OECD, OFID, IRENA, OSCE, ISTC etc.were located in one plaza. We had a small special stand inside this plaza with interactive computer where the video about ISTC and their partner countries was played. From the beginning till the end of the exhibition our stand never was empty because many people were really interested in ISTC. And now after finishing volunteering I want to thank ISTC for hiring me as a volunteer because I found a lot of advantages in this. Firstly, I had a chance to improve my English speech because I met a lot of foreign tourists and talked with them. I think that speaking with native speakers is more effective than other practices. Secondly, certificate that confirms that I was a volunteer has a good impact to my social life.Being a social active person is valued in university. Thirdly, this summer was incredibly cool and full of interesting things. During the work I met new friends, received different gifts and saw national day performances of several countries. I am eternally grateful to ISTC for providing opportunity to be a volunteer and I want to wish more achievements in the future as well.