The translations of the sample phrases you received are more or less correct. Of course, a whole bunch of things aren't covered yet such as "it's for an advertisement for ...", "the photoshoot/recording will take place at ... on ...", "you'll be expected to wear ..." and "I'll pay you ... yen." Even with those out of the way though, you presumably still won't be able to understand, much less answer, any further questions they might have. How do you intend on handling this?
Maybe it would be easier to start off the conversation with one simple "sumimasen, eigo ga hanasemasu ka" ("Excuse me, do you speak English?").