Nextion code problem ?

Hello together,

i have a weird problem with my arduino-Nextion project.

Till now i had warning if the water-tank of my project was empty.
For this i had this code:

/*
//sendet eine Warnmeldung an das HMI-Display sobald zu wenig Wasser im Tank ist:
if (digitalRead(Tanksensor)== HIGH)
{
Serial1.print("home.p2.pic=36");
SerialEnde();
Serial1.print("home.t0.txt=");
Serial1.print(""");
Serial1.print("Wasser auffuellen!");
Serial1.print(""");
SerialEnde();
WasserLow = true;
}
else if (digitalRead(Tanksensor)==LOW && WasserLow == true)
{
Serial1.print("home.p2.pic=2");
SerialEnde();
Serial1.print("home.t0.txt=");
Serial1.print(""");
Serial1.print("");
Serial1.print(""");
SerialEnde();
WasserLow = false;
}*/

Now i want to change the page instead of just a warning in the edge of the main page.

new code:
//sendet eine Warnmeldung an das HMI-Display sobald zu wenig Wasser im Tank ist:
if (digitalRead(Tanksensor)== HIGH)
{
page29.show();
WasserLow= true;
}
else if (digitalRead(Tanksensor)==LOW && WasserLow == true)
{
page0.show();
WasserLow = false;
}

Its also working. But the Problem is, it´s ultra slow.
As longer as i need to refill the water-tank, as longer the Nextion needs to change the page.
The first version with just the warning signal ist working 100% fine and fast.

I also tried it with: Serial1.print("page WasserLOW");
Also working but ultra slow.

Im talking about 3-10 seconds.
Somebody allready tried to Nextion pages with the Arduino?