Do your local road laws/inspection require your turn signals to be separated and yellow?
This does not look like an original factory install. Perhaps this light was installed at your Dealer/distributor when it was imported or by a Previous Owner and this person simply wired the lights together.
Confirm how this light is wired. Look under the back of the car at those lights. From your description:
the turn lights at the rear goes on at the same time as the brake lights when the break pedal is pressed
Sounds like you are saying:
-
Red Light
1 - Half Intensity when head lights activated
2 - Full intensity when Brake pedal pressed.
3 - Full intensity Flashing when Turn signal applied -
Yellow light
2 - Full intensity when Brake pedal pressed.
3 - Full intensity Flashing when Turn signal applied
I am guessing you want to remove function 3 from the red light, and remove function 2 from the yellow light.