Both the possessor and the possessed get an ending in Turkish. So "benim" is the 1st person possessive pronoun ("my"), and then -(I)m is the suffix for anything that's possessed by me.
There's a more complete explanation (with lots of examples) in the Possessives tips and notes: https://www.duolingo.com/skill/tr/Possessives
When one hovers over the word "benim" the pronunciation of the letters"be" is akin to "ba" in the English word "band," but when one plays the full sentence those letters sound more like the "be" in the English word "been." Is this because sounds in a string of words change because of the rhythm of the sentence?
It isn't really a word in Turkish (it probably used to be, but isn't anymore). It is kind of a root that means "there." If you are referring generally to a location, you can say "orası" and if you are taking about where something is located, you would say "orada." :)
Saying "over there" is the easiest way to emphasize the distance of "orada" and to differentiate it from "şurada" (which is not as far away). It's not mandatory, however, and a simple "there" works for both. :-)
I'm a beginner in German, so I can't confirm regarding "dort", but I know there are fluent and native-German speakers in this course. Hopefully one of them will stumble across this... I just didn't want to leave you waiting for the answer to your first question :-)
"over there" = "dort drüben" indicates a smaller distance, for example you point at your couch and say: "my cat is over there", "meine Katze ist dort drüben"
"there" = "dort" no specific distance, but needs context to work with more distant objects, for example you talk about a country and someone says: "my brother lives there", "mein Bruder lebt dort".