Server is too LAG

my server is too, no matter how many times I restarted, it still LAG . For an example, when I dug a stone, it still appeared in the same location, and it took several digs before it fell. Also, when I encountered creeper, it had already swelled to the point of exploding, but it exploded after a few seconds. I have checked my network and it is smooth. Is that a server problem?
The server is in aternos.com

PLS HELP, I cant play with my friend happily