Non-native speakers often make mistakes pronouncing the words multi and multiple in English. A possible reason is that these words have their origin in Latin, and hence are used in a number of other languages. The typical mistake involves an incorrect pronunciation of the letter u, listen here. Instead of pronouncing it as in the words cut or nut, it is pronounced as in full or pull. The correct pronunciations are [ˈmʌlti] and [ˈmʌltɪpl], listen here and here. An alternative pronunciation of multi common in American English is [ˈmʌltaɪ], with the letter i pronounced as the word eye, listen here.
A good example is the expression multiple choice. This term is widely used in German, but according to the Duden has kept its original, English pronunciation, see here. However, very often you can hear people pronouncing multiple as [ˈmʊltɪpl] instead of [ˈmʌltɪpl]. I believe that in most cases, this is an attempt to simplify the pronunciation, but next time I happen to overhear this mistake, I will ask the person how they pronounce multiple choice in English.