Is necessary close apps no iPhone?

No, it's not. Once you've stopped using an app, it goes into suspense until you want to open it again. If an app is using location services or is a streaming app, it may be helpful to close it. But generally speaking, apps not being used are not doing anything in the background.

Only if you are experiencing a problem with a specific app. There is no need to close apps to regain memory or to speed up your iPhone. Any app that is currently opened will have full access to all your resources on the device even it it needs to close an app that is suspended or stop a background process that an app may be allowed to run. This is automatically managed by the iPhone and requires no intervention on your part.

You're welcome.