Deleting apps running in background that I don’t want

To what end are you wishing to know this? Perhaps this article may help: Check the iPhone battery health and usage - Apple Support

Read the section: View your battery usage information

On your device go to Settings  > Battery.

Also go to Settings > General > Background app refresh. Decide which ones you do not need.

Unless it's something like a navigational or streaming app, it's not actually running in the background. it's suspended.