How do I make further progress?

I installed Terraria 4 days earlier (I play on mobile). I had no idea what to do so I just built a house and went for digging, except I don't know how to progress more. I only have iron tier armour. I got chance to fight the slime King but I overlooked the message as I was mining. Both sides of my world are filled with crimson. The things I want to ask is: 1. How to get more of your mining (and mining fast) 2. When and where to fight bosses 3. How to get better tiers

May you please see the loot I have and give me suggestions.