SpriteKit constant speed from left to right and left to right - swift

Question

i have a SKSpriteNode, that will move from left to right and right to left.
This is Speed
var currentPosition: CGFloat = 20
var rightSpeed = TimeInterval()
var leftSpeed = TimeInterval()
DidMove when SKNode start moving
override func didMove(to view: SKView) {
rightSpeed = moveToRightSpeed()
leftSpeed = moveToLeftSpeed()
personageMoving(position: currentPosition)
}
Method to start sequence of moving
func personageMoving(position: CGFloat) {
rightSpeed = moveToRightSpeed()
leftSpeed = moveToLeftSpeed()
let moveToRight = SKAction.move(to: CGPoint(x: UIScreen.main.bounds.maxX - 20,
y: -UIScreen.main.bounds.maxY + currentPosition),duration: rightSpeed)
let moveToLeft = SKAction.move(to: CGPoint(x: -UIScreen.main.bounds.maxX + 20,
y: -UIScreen.main.bounds.maxY + currentPosition), duration: leftSpeed)
let sequence = SKAction.sequence([moveToRight, moveToLeft])
let forever = SKAction.repeatForever(sequence)
personage.run(forever, withKey: "move")
}
This functions helps me to check speed
func moveToRightSpeed() -> TimeInterval {
let deltaX = UIScreen.main.bounds.maxX - personage.position.x
let deltaY = CGFloat(1)
let distance = (deltaX * deltaX + deltaY * deltaY).squareRoot()
let pixelsPerSecond = CGFloat(400)
let timeToTravel = distance/pixelsPerSecond
return TimeInterval(timeToTravel)
}
func moveToLeftSpeed() -> TimeInterval {
let deltaX = -UIScreen.main.bounds.maxX - personage.position.x
let deltaY = CGFloat(1)
let distance = (deltaX * deltaX + deltaY * deltaY).squareRoot()
let pixelsPerSecond = CGFloat(400)
let timeToTravel = distance/pixelsPerSecond
return TimeInterval(timeToTravel)
}
And in this method i ask person to go up, after it starts left to right and right to left again.
func personageGoUp() {
personage.removeAction(forKey: "move")
let moveLocation = SKAction.move(to: CGPoint(x: personage.position.x, y: personage.position.y + 100), duration: 0.2)
personage.run(moveLocation) { [weak self] in
guard let self = self else { return }
self.currentPosition += 100
self.personageMoving(position: self.currentPosition)
}
}
Problem is speed that is always changing, i can not understand how can i fix it