My iPhone 13 Pro Max doesn't charge above 80%

Hello.

I bought a iphone 13 pro max a few days ago and I use it with a apple original charger. but when the battery goes upto 80 percent the charging of the mobile gets stuck. First issue i facing is this.

And the second issue is that when I restart the phone after charging its battery percentage changes. This issue is not only on 80 percent . i face this issue everytime whenever i restart my phone after charging. Sometimes i charge my phone upto 60 or 70 percent only and whenever i restart my phone after charing the battery percentage increased by 2 to 5 percent. What is this issue? Please tell me the solution to this issue.

[Re-Titled by Moderator]