Howdy Crezaldy,
We understand the battery of your left AirPod doesn't last as long as the battery of your right one, despite using and charging them at the same time. You also stated that it seems like the sound quality of the left AirPod isn't as good as the quality of the right one. We'd like to address these issues.
Regarding battery life, check out the "Learn About Battery Life" expectations listed in this resource: Charge your AirPods and learn about battery life
The quicker battery drain on your left AirPod may be related to your microphone settings. If you notice this battery drain when using your AirPods on phone calls, you may need to adjust your them. You can do that by following the guidance in the "Set Microphone to left, right, or automatic" section of this article: Adjust the settings of your AirPods
You also mentioned sound quality. You may be able to address that by cleaning your AirPods. This article covers how to do that: How to clean your AirPods and EarPods
Finally, if these issues persist after adjusting settings and cleaning your AirPods, we suggest contacting Apple directly to explore your service options. You can start that process here: Get Support
To check the warranty status of your AirPods, check here: Check Your Service and Support Coverage
Cheers!
