You can use the Voice Memo app built-in iPhone to do some simple edits.
You can also use the third-party recording apps from the iPhone's App Store.
These apps can finish some professional audio edits.
You can choose a suitable app according to its features.

The voice memo app can trim, replace and delete part of a memo.
But when you need to learn a lecture recording or listen to a long meeting recording, an app should including the "Mark" function so that you can mark important moments at any time.
The voice memo app can not help you.

So it's easy to do a choice, find a piece of paper, write down
1. What you need an app for?
2. Which features you need?
3. Voice memo app features
4. Third-party apps features

For example:
1. Need an app for learning
2. Need the "Mark", Search, Trim, Change Pitch, Change speed, Insert, Share......

3. Voice memo app features: Search, Trim, Share
4. Voice Recorder Pro - Recordin‪g‬ app features: "Mark", Search, Trim, Change Pitch, Change speed, Insert, Share......

After comparing you can make the decision.

The voice memo is free but features less.
Some basic features of the third-party recording apps are free, some features need to pay, but features rich.

Have you chosen a suitable voice recorder app on your iPhone?
Share your ideas!