My World is freezing

Game is lagging in one map, which we playing about a year with friends. about every 10 seconds game freezing and it's terrible to play now. But if i start new map - everything is ok. But we don't want to play new map, we want to play this.

It will be very cool if you help us, I can send my world (400mb), and I know that you can fix it, help us please! Or say how I can fix it by myself - we need it so much!!