Error in code

Trying to implement this code but I'm missing an error. I guess it has to be with my conditions, but I have not figured it out the solution.

#include <Servo.h>

Servo servoLeft;
Servo servoRight;
#define downbutton 7
#define upbutton 9

void setup() 
{ 
  servoLeft.attach(3);
  servoRight.attach(5);
  pinMode(downbutton, INPUT);
  pinMode(upbutton, INPUT);
}

void loop() {
 int buttonstate1 = digitalRead(downbutton);  // Two States for buttons
 int buttonstate2 = digitalRead(upbutton);
 int pos = 20;
 int neg = 70;
 int pos2 = 20;
 int neg2 = 70;
for(pos < 70; pos += 5; neg > 20; neg += -5){ // goes from 0 degrees to  110 degrees and viceversa in steps of 5 degree
   if(buttonstate1 == true){ //button is high
   servoLeft.write(pos); // tell servo to go to position in variable 'pos'
   servoRight.write(neg); // tell servo to go to position in variable 'neg'
   delay(1000); // wait 1 second
  }
} 
for(pos2 < 70; pos2 += 5; neg2 > 20; neg2 += -5){ // goes from 0 degrees to  110 degrees and viceversa in steps of 5 degree
   if(buttonstate2 == true){ //button is high
   servoLeft.write(neg); // tell servo to go to position in variable 'neg'
   servoRight.write(pos); // tell servo to go to position in variable 'pos'
   delay(1000); // wait 1 second
  }
} 
}
for(pos < 70; pos += 5; neg > 20; neg += -5){

Is not C/C++ syntax.

Perhaps you meant

for(; pos < 70 && neg > 20 ; pos += 5, neg += -5){
  for (pos < 70; pos += 5; neg > 20; neg += -5)

Can you please explain what this for loop is intended to do ?

Do you mean it to vary the value of both pos and neg and, if so, in what order ?

It intend to slow the movement of two servos at the same time. They are oriented in opposite directions, that's why it has different values.

that's why it has different values.

A for loop has ONE index. How you USE that value in the body is up to you. RTFM on the for statement.