Well, it's not quite deep in the throat. The sound of ص is like "S" but with more room for air inside the mouth. To my knowledge in IPA (International Phonetic Alphabet) both sounds of س and ص are considered "voiceless*. Which means, the vocal cords do not vibrate when they are spelled out.
For the sound of ص just try to say regular "S" as in English, and while you say it repetitively, try to close your teeth together completely, and this might help on curving the middle of your tongue downward a bit. You should notice that the sound of "S" is becoming "heavier" as if more volume of air is passing through your mouth. This is what is called sometimes a "broad" sound, where a letter can have two different ways in spelling, slender and broad, or soft and hard as in the case of Russian where signs like ь and ъ are used respectively to note soft and hard pronunciation for such letters. In Arabic, though, the change in softness and hardness, mostly produce another letter completely (which changes the meaning completely sometimes), as is in the case of س and ص.
As for ق, well this one comes from the throat or around the throat (can't remember the exact anatomical name for the part issuing this sound in the throat, but I think it is the uvula). Mostly, non-Arab learners would associate the sound of this with "k", and indeed, many of them do flip it to "K". Many Asians, like Filipinos, do have this sound already in their language "probably written as (G)". Anyway, as a starting tip, try to say "K" repetitively, and then slowly try to push the source of "K" sound (or the click that produces it) backward. The sound of "K" is mostly produced by a click of the tongue against the roof of the mouth somewhere at the back of the mouth, and "Q" or ق is further back down to the throat.
Hope that helps!
First of all: Friend = cadíq صديق (I just like to use C instead of S for this sound and í instead of ii).
The basic word is (cadíq). However, the declensions or the changes on the word that shows the word status (nominative, accusative, dative ...etc) appear at the end of the word. Since (cadíq) is in nominative status here (normal status, nothing affecting the word) then it takes the sign (-u) and becomes (cadíqu).
After this change, the possessive suffix (-hu) which means (his) is added, so the word becomes (cadíquhu).
Just to extend this more, let's suppose a case of accusative, as in the sentence: I see his friend (أرى صديقَهُ) = ará cadíqahu.
Notice how (cadíq) this time took the last vowel (-a) because the word now is in accusative status (for the verb أرى I see); Then the possessive suffix (-hu) is added.
I hear a brief fricative, like the french R, just before the "q". Am I alone? And I think it's not the first time. What I mean is that the "q" isn't a clean plosive, as presumably it should be... Hey! I just found this about qaaf in Wikipedia: "In some languages the vocal cords are actively separated, so it is always voiceless; in others the cords are lax, so that it may take on the voicing of adjacent sounds." That would explain the slight French-R sound, which is also very similar to ghayn. The link to the article is https://en.wikipedia.org/wiki/Voiceless_uvular_stop#:~:text=The%20voiceless%20uvular%20stop%20or,used%20in%20some%20spoken%20languages.&text=The%20symbol%20in%20the%20International,X%2DSAMPA%20symbol%20is%20q%20.
Ah, OK. Shame. That went so well with what I found on Wikipedia. But I think people do seem to hear different things from the same audio on Duolingo... Actually, I think I'd heard that sort of sound before with qaaf. I'll listen very carefully in future. Thanks for responding.
Well, then it seems the audio system. Just to make sure, maybe you can use another system (headphone, speakers, or even another device if possible) to see if there is still a fricative sound. Qaf is definitely plosive and even though it's a speech-machine and not a real person that spells words on this course (so there is always a probability of mistakes), but personally, I don't hear any fricative sounds before (Q) in cadíquhu.
Try with a headphone if possible it might make the sound clearer. I'm on PC here and using speakers. It could be also that sometimes our brains trick us with unfamiliar sounds and assign those to familiar sounds that we can understand - I've seen such case with many people here listening to the sound of ط ... many users reported that they hear (P) and the fact that (P) is labial and ط is not, makes me think that it's just the mind's game to assign sounds to something that a person is familiar with. It might take some time to get familiar with new sounds, I guess.