Use simple English as if you're trying to communicate with a Caveman (but while acknowledging many of them are fairly intelligent aside from the language barrier).
Don't use slang; slang do not translate. You wouldn't tell a cavewoman "You give head!" because it doesn't make sense. Remember, any English phrase you say to them they have to convert into their native language in their head first, then try to parse it.
Blowjob would also be a slang and probably just as confusing since there's no blowing action. It might be common enough that they may have heard it (as opposed to "give head") but why use it if you already know there's a language barrier.
Want BJ? Point to your dick and say "Mouth?" They're not actually cavewoman, so they're smart enough to infer from that as long as you keep it to simple English.
Want/don't want condom? I think "cover" and "protection" generally works, but bear in mind not all providers are ok with that. Many places is a BYOC setup so communicate accordingly; they may not be willing to give you BJ or FS at all if you didn't BYOC.
For anything else like cuddling, 69, etc. as a last resort you can always say "I show you" to get implicit permission to just move each other around to get in position.