if lu guang is from china originally and speaks chinese as his first language but has travelled to bridon multiple times in different timelines it means that lu guang must’ve picked up the language not only to understand what vein, liu xiao, and xia fei are saying but to actually communicate with them in english in an english speaking country where they can be overheard and understood
this could also be a reason of why vein, liu xiao, and xia fei know he’s gone back in time because cxs and lg spend a lot of time together and cxs doesn’t understand a word of english (and you’d think cxs would be suspicious that lg knows it well enough but not him)
additionally, maybe lg gave cxs false information on what vein said to possibly show to vein that he’s in fact not fluent in the language or doesn’t fully understand english yet so they don’t think he’s gone back enough times to pick it up