xxxx ticks behind

 Hallo,

I'm sorry, my english is not good.

It doesn't matter, if i play survivaloder creative. The game ist stopping. I mean, i can not play fluently. When i end the game there are warnings: Can't keep up. Is the server overloaded?  Running xxxx ms or xxx ticks behind.

I need help. But in easy words. I'm also not good in things of PC