Server issues

After my friends and I joined my server, it starts lagging and saying "can't keep up! server is overloaded! " , and then it crushed. I tried to rejoin my server for 5 times, and it crsuhed for 5 times. I'm very sure that I created the server correctly because first, I can join the server, it crushed after I join it. Second, I created it the same way as I created a 1.15.2 server that is working. So I'm wondering if this is a bug for 1.16 servers.