Little laggy and glitchy and wither skeletons are broken

The world its a little lag and small glitch and the wither skeletons are slow to jump on block and run.

Seed: -106439012 

Oh!! And the drowners are broken they don't swim good even when some of them has the trident but it takes 10 sec to shoot. Please mojang and even its not an old phone I buy it in 2 months and its LG k20 plus.