Chunks not loading fast as I see it

So I am playing on a friends world on my PC, and I am wondering why the chunks don't load fast enough, every time I break blocks they keep reappearing 2 or 3 times and when I build blocks they keep disappearing, I also get this issue with an endermen attacking me but I don't see it. Also a player joined an he told me that he keeps getting laggy not sure what this issue may have overcome.