How can you tell if your iPhone has been compromised?

Neither of those symptoms indicate being hacked, its just glitching.

Try a forced restart.

• Press and quickly release the volume up button

• Press and quickly release the volume down button

• Press and hold the side button.

• When the Apple logo appears, release the button.

Force restart iPhone - Apple Support (IN) Force restart iPhone - Apple Support (IN)

If you think your Apple ID is compromised, use these steps to gain control of it and review your account information:

1. Sign in to your Apple ID account page . ...
2. Change your Apple ID password and choose a strong password.
3. Review all the personal and security information in your account. ...
4. Check with your email address* provider to make sure that you control every email address associated with your Apple ID. ...
5. Set up two-factor authentication for your Apple ID. ...

If you think your Apple ID has been compromised

If you feel an unauthorized person is remotely controlling or monitoring your device, then that is possible only if you have done one or more of the following Don'ts...

1. Don't hand over an iPhone to kids or to a stranger without Enabling Guided Access
2. Don't share Apple IDs
3. Don't Jailbreak
4. Don't share sensitive information pertaining to your device
5. Don't give in to Phishing
6. Don't leave your iPhone unlocked and unattended in public places like offices, schools, malls etc.

Keep the iPhone updated to the latest iOS always and never Jailbreak. That's it.

iOS / iPadOS devices cannot be hacked or infected with Virus / Malware / Spyware if it is updated to the latest iOS/iPadOS unless you have intentionally downloaded spurious software or unauthorized apps directly from the internet and installed them on your device or/and have Jailbroken. 

It (Hacking) also depends on how careful you are in sharing sensitive and valuable information pertaining to your iPhone such as Passcode, Password, etc with your friends and family members.

Be judicious when sharing the device's sensitive and valuable information with friends and family members.

If you don't reckon what is said above is true then you have two options...

1. Report the hacking incident that you are facing to the local law enforcement authorities and follow it up
2. Believe it, it can't be hacked. There are people who still believe that the earth is flat and also some believe no one has ever landed on the moon. What can anyone do about that? This is a free world you can believe in anything, choice is yours.

JEDunnam83 Said:

"How can you tell if your iPhone has been compromised?: I think my iPhone 13 Pro Max has been compromised. How do I check to see if it has been hacked? How do I check to see if it has had a virus put on it? my keyboard is weird. It has 2 buttons that are a sky blue color. They don’t go off that color. My screen resolution is not crisp and clear. It is static looking. Not like other peoples"

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Thank you for the screenshot.

Troubleshooting a "Hacked" Device:

Just like anyone, your best options are to secure your account (open and use a new eMail address for your Apple ID), and add everything manually. As for your current phone, set it up anew, as if you were to sell it.  In Depth.

Four Things Here:

A. Modify your Credentials:

Having so much suspicion, consider modifying your credentials, ASAP, starting with a new password.

• Modify: your login credentials (using both a New eMail and a New Password) for Apple and each and all sites
• Associate: a different method of payment to your account
• Enable: Two-Factor Authentication for Apple ID PayPal and for all other accounts that have such an applicable option

B. Verify Your Devices:

Verify that your the devices logged in to your account or officially yours, by using this link: Check your Apple ID Device List to See where you're Signed in - Apple Support

C. Report this to Apple:

Have any suspicious items on the screen (i.e. messages)? Use my User Tip: Using the Photos App to Report Scams: - User Tips

and...

D. Set this Up Anew:

If you are so concerned, then reset your iPhone, as if you were to sell it. Perform as interacted here, including the backup: What to do Before you Sell, Give Away, or Trade in your iPhone, iPad, or iPod touch - Apple Support

iPhone cannot be compromised but Apple ID can be.