If you want to speak to someone you need to share a language. Because languages have different phonemes it can be difficult to pronounce a foreign language.
So how about if we all had a base of sign language that we could communicate with? The advantage is simple movements do not have a local accent that localises them.
So how many words do you need to know?
Language word usage follows zipfs law. Which means a suprisingly low number of words cover a high percentage of our speech.
There are 850 words in basic english which implies you can communicate basic information with about this many words.
Newspeak the artificial language in the novel 1984 was simplified to the extent to make coherent political thought impossible. The point of here is to search for a simple universal language is for emergency situations or for providing an anchor for language learning so such a Newspeak nightmare is not a worry.
One way of looking for a basic subset of language is to find the common subset of all languages. This has been studied as the semantic metalanguage. There follows a list of the words (in english) that occur in all known languages and their international sign language equivalant.
The English exponents of the 61 Semantic Primitives (addition of LONG is proposed)
actions, events and movement
existence and possession
A LONG TIME
A SHORT TIME
FOR SOME TIME
BIG, SMALL, (LONG)
KIND OF, PART OF;