My phone needs help.

My phone had been acting up lately.(Samsung S6)

-Sometimes when i turn my phone phone off and switch it on my battery percentage decreases by at least 48%. eg(my phone was on 65. I decided to restart it and it went down to 13%. I think i need a new battery

-my recent key has been pressing on itself every 2 seconds

-the back of my phone has cracked and the glass infront of my rear camera is broken

How much will it cost me to fix my phone?