About the English Windows-- After you get to a Chinese website, right-click anywhere on the web page, choose Ecoding-->Chinese Simplified. Windows then will tell you to download a patch from the Microsoft website. Do that and then install. You will be able to read Chinese just fine. Microsoft also has patches for Chinese input. You can find the patch on Microsoft website also.
Professional English-- No good advise there. But it is important to show them that you are what you said. Maybe spend more time after work to prepare? Maybe get a vender catalog to get familiar with all the material/supplies name. Or go to Home Depot (some kind of hardware store) to see what are the names for construction material/ supplies.
Good luck! The beginning is always hard, but you want to make sure they keep you after the trial peirod. I will be in touch if you need help. Roger will know most of the common terms for construction.