Multiple buttons/inputs how to?

I´m trying to make a sequential tail light to my mustang.
My tought is to make the 6 bulbs (3 left and 3 right) "running" when braking. Thats about how far I´ve come.

But when turning on turnsignal to left or right I want that input to override the brakeinput and start the turn signal.

So on my breadboard I have 6 leds connected to I/O 3-5 (right side) and I/O 10-12 (left side) Button for "left turn" on I/O 8 "brake" on I/O 7 and "right turn" on I/O 6

I get running lights when "braking" but then I´m stuck. I know I can use arrays and other fancy stuff for the leds but I´m a total beginner so I try to keep it simple.

int switchstate = 0;

void setup() {
  // declare the LED pins as outputs
  //  pinMode(2, OUTPUT); //not in use right now
  pinMode(3, OUTPUT); //Right led 3
  pinMode(4, OUTPUT); //Right led 2
  pinMode(5, OUTPUT); //Right led 1
  pinMode(10, OUTPUT); //Left led 1
  pinMode(11, OUTPUT); //Left led 2
  pinMode(12, OUTPUT); //Left led 3
  //  pinMode(12, OUTPUT); //not in use right now
  pinMode(6, INPUT); //right turn
  pinMode(7, INPUT); //brake
  pinMode(8, INPUT); //left turn
}

void loop() {

  switchstate = digitalRead(7);

  // if no button is pressed
  // just tail lights
  if (switchstate == LOW) {
    digitalWrite(3, HIGH);
    digitalWrite(4, LOW);
    digitalWrite(5, LOW);
    digitalWrite(10, LOW);
    digitalWrite(11, LOW);
    digitalWrite(12, HIGH);

  }
  else {
    digitalWrite(3, HIGH);
    digitalWrite(4, LOW);
    digitalWrite(5, LOW);
    digitalWrite(10, LOW);
    digitalWrite(11, LOW);
    digitalWrite(12, HIGH);

    delay(200);
    digitalWrite(3, HIGH);
    digitalWrite(4, HIGH);
    digitalWrite(5, LOW);
    digitalWrite(10, LOW);
    digitalWrite(11, HIGH);
    digitalWrite(12, HIGH);

    delay(200);
    digitalWrite(3, HIGH);
    digitalWrite(4, HIGH);
    digitalWrite(5, HIGH);
    digitalWrite(10, HIGH);
    digitalWrite(11, HIGH);
    digitalWrite(12, HIGH);
    delay(200);

    digitalWrite(3, LOW);
    digitalWrite(4, HIGH);
    digitalWrite(5, HIGH);
    digitalWrite(10, HIGH);
    digitalWrite(11, HIGH);
    digitalWrite(12, LOW);
    delay(200);

    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
    digitalWrite(5, HIGH);
    digitalWrite(10, HIGH);
    digitalWrite(11, LOW);
    digitalWrite(12, LOW);
    delay(200);

  }
}

add:

 if (digitalRead(6)== LOW) // right
 digitalWrite(lightpin1, !digitalRead(lightpin1))  //change status on this bulb
 delay(short time);
{

..similar for other direction

Sloppiness aside, what should the break, left and right sequences look like?

describe HOW, exactly, this shall work.
lamps BL B1 B2 ----- B2 B1 BR (blink left / brake / break ---- brake / break / blink right
situations:
Normal driving: B2 lit ?
Breaking only: BLR/B1/B2 - runs fast sequence ? (one lit at a time or overlapping run?)
Blink only: B2 lit, BL/R blink 700ms ON 300 ms OFF (1 second rate)
Blink and break: BL/R blinks as usual, B2,B1 ??
Draw to timescale or describe..