In American accent, almost all vowels in non-stressed syllables and non-diphthong containing syllables can be reduced to schwas in non-careful everyday speech. Example: In 'easier to understand', 'to' and the first syllable of 'understand' are pronounced with a schwa. It is fully explained in detail in Ann Cook' book American Accent Training. In another cases we can completely delete the schwa vowel as in the first syllable of 'photography'. This feature reflects more the natural way of spoken informal standard language (language used on T.V/in universities/by educated people/by strangers).
So in comparison, in non-careful casual everyday German speech, can vowels in all non-stressed syllables (excluding those which contain diphthongs!) be reduced to schwas? Which non-stressed syllables vowels cannot be reduced to schwas? Can we render the vowels in the bold syllables in the next examples to schwas?
Computer, Deutschland, bedeutsam, bedeutunngsvoll, spezifizieren, Heimat, Wahrscheinlich.
Schwa is the most neuter unstressed vowel in German as well as in English, its sign in the phonetic alphabet is 'ə'. The same vowel in the end of words like 'Hunde, Bleibe'. In the course of everyday fast uncareful talking, many vowels may lose their original quality and tend to be more centralized with less force and finally become schwas. Germans use this vowel a lot. In English, it is the most used vowel at all.