Refine storage-extention.md (#6885)

docs/en/guides/storage-extention.md

 # Extend storage
 SkyWalking has already provided several storage solutions. In this document, you could 
-learn how to implement a new storage easily. 
+learn how to easily implement a new storage. 
 
 ## Define your storage provider
-1. Define a class extends `org.apache.skywalking.oap.server.library.module.ModuleProvider`.
-2. Set this provider targeting to Storage module.
+1. Define class extension `org.apache.skywalking.oap.server.library.module.ModuleProvider`.
+2. Set this provider targeting to storage module.
 ```java
 @Override 
 public Class<? extends ModuleDefine> module() {
@@ -13,7 +13,7 @@ public Class<? extends ModuleDefine> module() {
 ```
 
 ## Implement all DAOs
-Here is the list of all DAO interfaces in storage
+Here's a list of all DAO interfaces in storage:
 1. IServiceInventoryCacheDAO
 1. IServiceInstanceInventoryCacheDAO
 1. IEndpointInventoryCacheDAO
@@ -40,12 +40,11 @@ Here is the list of all DAO interfaces in storage
 1. IProfileThreadSnapshotQueryDAO
 1. UITemplateManagementDAO
 ## Register all service implementations
-In `public void prepare()`, use `this#registerServiceImplementation` method to do register binding your implementation with the above interfaces.
+In `public void prepare()`, use `this#registerServiceImplementation` method to register and bind with your implementation of the above interfaces.
 
 ## Example
-Take `org.apache.skywalking.oap.server.storage.plugin.elasticsearch.StorageModuleElasticsearchProvider` 
-or `org.apache.skywalking.oap.server.storage.plugin.jdbc.mysql.MySQLStorageProvider`  as a good example.
+`org.apache.skywalking.oap.server.storage.plugin.elasticsearch.StorageModuleElasticsearchProvider` and `org.apache.skywalking.oap.server.storage.plugin.jdbc.mysql.MySQLStorageProvider`  are good examples.
 
-## Redistribution with new storage implementation.
-You don't have to clone the main repo just for implementing the storage. You could just easy depend our Apache releases.
+## Redistribution with new storage implementation
+To implement the storage, you don't have to clone the main repo. Simply use our Apache releases.
 Take a look at [SkyAPM/SkyWalking-With-Es5x-Storage](https://github.com/SkyAPM/SkyWalking-With-Es5x-Storage) repo, SkyWalking v6 redistribution with ElasticSearch 5 TCP connection storage implementation.