Cannot control servo with button.
The problem is that servo1.write(90) does not do what you think it does.

servo.write(angle) tells the servo to go to that position, not to move by that many degrees. What you need is to set one angle when the button is not pressed, and a different angle when the button is pressed.

Normal hobby servos can move about 180 degrees. Where 0 is depends on how the servo horn is positioned. Which direction of rotation is positive depends on the manufacturer. 

try something like this to set one position when the button is pressed and a different one when it is not:

if (button1State == LOW);{
    servo1.write(45);  // move servo
}
else {
    servo1.write(135);
}