ender dragon invincible against arrows and being very slow

1.)I once wanted to fight the ender dragon, so I got everything I needed to fight it. When I got to the end, I shot the dragon with arrows but it did nothing. so I only used melee attack to defeat him

2.)Yesterday, I went to the end again and I noticed the dragon was ultra slow. It took 8-9 secs to pass an entire pillar. Also, can Mojang please add the nether update to ps4 bedrock, please?