I wANT TO IMPROVE MY eNGLISH

Good evening, ladies and gentlemen. I registered to this site today afternoon because I want to go to work in Switzerland for my company, and one of the requirements is fluent English.
I studied English at high school and now there have been many years that I haven't spoken this language. I believe it will be particularly difficult understanding the speech. Could someone help me to do practice?
Thank you!