How much it cost to get the front screen & back , the battery fix?

@sesmar8263 that is a very subjective question and you can get tons of different answers. Since we are not in the habit of suggesting any kind of outside vendors you want to check the iFixit business partners on here https://www.ifixit.com/Business These are people that have proven that they are trustworthy and reliable. In short, they have the iFixit community stamp of approval.

Remember, iFixit empowers you to do your own repairs. Use the guides for the repairs that your phone needs, from here iPhone 12 Pro Max Parts are also available on here. the cost for that repair will then only be what the cost for the parts is.