My iPhone apps all get slow and laggy when I try to open them sometimes, there’s a black screen for a few minutes and I can’t press anything. Sometimes while I’m texting it will boot me out and go to black screen, my FaceTime calls also randomly fail

Hi ason288

welcome to the Apple (user-to-user) Community.

Wondering if you have enough memory / storage free (Eg at least 8Gb free) for your iPhone to operate smoothly.

How to check the storage on your iPhone and iPad - Apple Support

If needed: See: "Manage space on your iPhone, iPad, or iPod touch” in the article below

If you need more space for an update on your iPhone, iPad, or iPod touch - Apple Support

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If memory / storage is not causing the difficulty:

Check if you have any third-party (non-Apple) apps that may cause interference ... eg ad-blockers, unnecessary virus checkers, cleaners, and the like ... even VPN can be a source of problems ... or apps that have not been updated to remain compatible with recent Apple updates. Eg: If you have such apps, try turning them off, and see if any have been causing your difficulties.

Wondering which apps are the ones slow to load : could it be apps (eg Safari) that use the internet.

Eg: You may need a strong wi-fi signal for FaceTime etc.

All the best :-)

ason288 Said:

"My iPhone apps all get slow and laggy when I try to open them sometimes, there’s a black screen for a few minutes and I can’t press anything. Sometimes while I’m texting it will boot me out and go to black screen, my FaceTime calls also randomly fail"

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Troubleshooting Lagging iPhone:

Clear Space.

Clear Space Using my User Tips:

Internal service may be swollen up through use of little space remaining. So, clear items...

• How to Clear Space from your Mobile Device, and What to Clear: - User Tip. You may have too much installed, and need to clear space. So, see my user tip: 
• How to Clear "Other" in your iPhone's Storage - Use Backup - User Tip. Caches would be being used for remembrance of application use. It is essentially the same for an iPhone. You'd backup your iPhone, and then restore your iPhone from the backup you've just created. All System Data will delete.