use two lines of events to do the centerprint
the box after the text is how long it will display in seconds, if you want each message to be displayed for 5 seconds, set it to a second longer
put the second message on the second event line, delayed by however long you want each message to be delayed for, in this case 5000, and set it to last for 5 seconds
the second event will overwrite the message being displayed, the longer duration on the first event is to prevent any flickering if it lags for a moment before getting to the second event
example:
[0] input > client > centerprint [message A] [6]
[5000] input > client > centerprint [message B] [6]
[10000] input > client > centerprint [message C] [5]
this will display message A for 5 seconds, then message B, then message C