I want a message to remain on the lcd screen until some data is entered, with the delay I only have to enter the fast data and that is not what I want
This is not an Installation and Troubleshooting question.
2)
Nothing is urgent on a forum.
3)
You have existing code; show it.
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In setup(), dump the message on the screen.
In loop(), wait for data to be received and remove the message from the screen.
If that does not exactly do what you want, I think that you need to read up on finite state machines.
An LCD display will display the message you tell it to display until you disconnect the power or tell the display to display something else (or nothing).
And if you want the message to remain on the 'display' even when you turn it off, use an ePaper display.