I put "these trees bear oranges" and it was marked wrong. I wonder, had I put "these trees are bearing oranges" would that have been more acceptable, or is the fact that trees bear fruit, rather than having fruit not part of Duo's database? OK, I tried "are bearing" and Duo doesn't accept that either. Pity. In English English, trees don't "have" fruit - that does sound foreign. Trees "bear" fruit. Duo should include that, it is better English.
If a person heard/read this German sentence, how would they know if the speaker/writer meant "those" or "these"?
diese means "these"
If the person had said die, then either "these" or "those" could be meant. If the speaker wanted to be more specific, they could have said die ... hier or die ... da.
But often it's not that important.
Much as English generally doesn't distinguish between "those (near you)" and "those (far from both of use)", though e.g. in Japanese those would be two separate words (sono, ano).
Pronunciation wise is the a difference between 'Diese' and 'Dieser'?
Yes: [ˈdiːzə] versus [ˈdiːzɐ].
The first word ends in a shwa (a neutral vowel pronounced in the middle of the vowel space), while the second word's final vowel is pronounced with your mouth wider open, closer to [a].
How rhotic is German?
The unstressed final sequence -er is [ɐ].
Otherwise, r after a vowel (in the same syllable) is usually [ɐ̯], e.g. vor [foːɐ̯]. The sequence ar may sound simply like a long a, e.g. Quark rhyming with Tag.
Some people (especially in the west) pronounce r as a consonant between a vowel and p t k, e.g. Sport [ʃpɔxt] (with r, nominally /ʁ/, assimilating to a voiceless [x] before the voiceless [t]). That's distinctively regional, though.
So r is pronounced as a consonant usually only at the beginning of a syllable, not at the end of one.
Diese can mean this these when do you know the differebce
You look at the following word.
Bäume is plural, so in English you have to say "these trees" for diese Bäume.
With a feminine noun such as Katze, diese Katze translates to "this cat".
In short: use "this" before a singular noun in English, "these" before a plural noun.
So diese is the plural of das?
No. It's the plural of dieser, diese, diese.
The plural of der, die, das is die.
And can be used for any gender words?
There is no gender distinction in the plural in German.
So we have diese Männer, diese Frauen, diese Kinder "these men, these women, these children" and die Männer, die Frauen, die Kinder "those men, those women, those children".