Just one of break lights on right side on audi q7 2008 does not working...where is fuse for that?

Check the fuse first!
Its in the main fuse box!

http://www.audihowto.com/audi-a6-c6-2004-2011-fuse-box-location-and-fuses-list/

It could be the switch. But first pull the DRL (day time running lights) relay or fuse from the fuse panel. Check the lights again. If it still does it, replace the switch. If it works right, then you need to have the BCM (body control module) scanned to see what's wrong.

do the turn signals use the same bulb as the break lights ???
suspect a turn signal switch

You didn't mention the obvious, fuses. In many euro cars there are multiple fuses for each light circuit, side to side, and inside to outside, so check fuses, even if it looks good, they can still be bad. Switch with same amp and color fuse with any other same specs to narrow it down. Fuses can be tricky believe it or not, and I can't tell you how many times people overlook the obvious, even mechanics.
Good luck,
FREE-BUSINESSES.com

Most likely this is not a fuse if it is just one headlight. Replace the headlight bulb and that should resolve the issue. If you have already done that start checking the wires for shorts or breaks and test the light switch itself.

you have a bad ground to the rr taillight assembly

Fuses: Fuse arrangement in fuse panel, behind instrument cluster, left
Fuse Arrangement In Fuse Panel

1 - Heated washer jets 5A 2 - Turn signals 10A 3 - Headlight washer (relay), illumination for glove
compartment, climate control, Automatic Transmission, instrument cluster 5A 4 - License plate light 5A 5 - Instrument cluster, seat heating, test connection
for cruise control, bulb monitor for auto-check display, Automatic Transmission display, switch
lighting, mirror switches and actuators, airbag
warning light, outside temperature indicator,
climate control 10A 6 - Central locking system 5A 7 - Anti-lock brake system (ABS) 10A 8 - Vacant 9 - Mirror heating 10A 10 - Vacant 11 - Cruise control (Automatic Transmission) 5A 12 - On board diagnostic system 10A 13 - Brake lights 10A 14 - Interior lights, reading lights, anti-theft alarm system, vanity mirror 10A 15 - Instrument cluster, power windows, climate control, automatic transmission 10A 16 - Anti-lock brake system (ABS), Anti-Slip Regulation (ASR) 5A 17 - Heated door locks 10A 18 - High-beam, right 10A 19 - High-beam, left 10A 20 - Low-beam, right 15A 21 - Low-beam, left 15A 22 - Side marker and tail light, right 5A 23 - Side marker and tail light, left 5A 24 - Wiper and washer system 25A 25 - Blower for heating, climate control 30A 26 - Rear window defogger, mirror heating 30A 27 - Rear window wiper 15A 28 - Fuel Pump 15A 29 - Engine timing 30A 30 - Sun roof 20A 31 - Tail lights, cruise control, automatic transmission 15A 32 - Engine timing 20A 33 - Cigarette lighter 15A 34 - Engine timing 15A 35 - Trailer recptacle 30A 36 - Fog lights 15A 37 - Radio 20A 38 - Luggage compartment light, central locking system 15A 39 - Emergency flasher system 15A 40 - Horn 25A 41 - Anti-lock brake system (ABS) 25A 42 - Vacant 43 - Vacant

Break light switch on the break peddal under the dash or light bulbs in the tail lights.

sounds like bad fuses or bad fuse circuit bord.
Jeremy...