all that glitters is not gold(things that appear valuable or worthwhile might not actually be so) phrase [UK: ɔːl ðæt ˈɡlɪ.təz ɪz nɒt ɡəʊld] [US: ɔːl ˈðæt ˈɡlɪ.tərz ˈɪz ˈnɑːt ɡoʊld]
bàixù qízhōng/ noun
fly in the ointment(something which ruins or spoils everything else, or makes it less pleasant) noun [UK: flaɪ ɪn ðə ˈɔɪnt.mənt] [US: ˈflaɪ ɪn ðə ˌɔɪnt.mənt]