Hi there, HashiMCT,
Welcome to the Apple Support Communities!
We understand that you're not hearing any alerts for your notifications and your apps are loading slower than they used to.
First, we'd recommend that you check the Ring/Silent switch on the side of your iPhone to ensure that it's on Ring mode. You can learn how here: How to put your iPhone on vibrate, ring, or silent mode
This is also a great resource which will help you to isolate the apps opening slower than you'd expect: About iOS performance on your iPhone, iPad, or iPod touch
Let's also make sure that you have installed all app updates: Update apps or use automatic downloads
Check your notification settings for each app you are having issues with: Use notifications on your iPhone, iPad, and iPod touch
Ensure that Do Not Disturb is not turned on: Use Do Not Disturb on your iPhone, iPad, and iPod touch
Is the date and time correct on your device?
If you are using any VPN connections, turn it off and test.
We hope this helps.
Cheers!