Refine service-agent doc (#7638)

docs/en/setup/service-agent/browser-agent.md

 ## Browser Monitoring
-[Apache SkyWalking Client JS](https://github.com/apache/skywalking-client-js) is client-side JavaScript exception and tracing library.
+[Apache SkyWalking Client JS](https://github.com/apache/skywalking-client-js) is a client-side JavaScript exception and tracing library.
 
-- Provide metrics and error collection to SkyWalking backend.
-- Lightweight, no browser plugin, just a simple JavaScript library.
-- Make browser as a start of whole distributed tracing.
+It has these features:
+- Provides metrics and error collection to SkyWalking backend.
+- Lightweight. No browser plugin required. A simple JavaScript library.
+- Browser serves as a starting point for the entire distributed tracing system.
 
-Go to the Client JS [official doc](https://github.com/apache/skywalking-client-js#quick-start) to learn more.
+See Client JS [official doc](https://github.com/apache/skywalking-client-js#quick-start) for more information.
 
-Note, make sure the [`receiver-browser`](../backend/backend-receivers.md) has been opened, default is **ON** since 8.2.0.
+Note: Make sure [`receiver-browser`](../backend/backend-receivers.md) is enabled. It is **ON** by default since version 8.2.0.

docs/en/setup/service-agent/server-agents.md

-## Language agents in Service
+## Installing language agents in services
 
-- [Java agent](http://github.com/apache/skywalking-java). Introduces how to install java agent to your service, without any impact in your code.
+- [Java agent](http://github.com/apache/skywalking-java). Learn how to install the Java agent in your service without affecting your code.
 
-- [LUA agent](https://github.com/apache/skywalking-nginx-lua). Introduce how to install the lua agent in Nginx + LUA module or OpenResty.
+- [LUA agent](https://github.com/apache/skywalking-nginx-lua). Learn how to install the Lua agent in Nginx + LUA module or OpenResty.
 
-- [Kong agent](https://github.com/apache/skywalking-kong). Introduce how to install the lua agent in Kong.
+- [Kong agent](https://github.com/apache/skywalking-kong). Learn how to install the Lua agent in Kong.
 
-- [Python Agent](https://github.com/apache/skywalking-python). Introduce how to install the Python Agent in a Python service.
+- [Python Agent](https://github.com/apache/skywalking-python). Learn how to install the Python Agent in a Python service.
 
-- [Node.js agent](https://github.com/apache/skywalking-nodejs). Introduce how to install the NodeJS Agent in a NodeJS service.
+- [Node.js agent](https://github.com/apache/skywalking-nodejs). Learn how to install the NodeJS Agent in a NodeJS service.
 
-The following agents and SDKs are compatible with the SkyWalking's data formats and network protocols, but are maintained by 3rd-parties.
-You can go to their project repositories for additional info about guides and releases.
+The following agents and SDKs are compatible with SkyWalking's data formats and network protocols, but are maintained by third parties.
+See their project repositories for guides and releases.
 
 - [SkyAPM .NET Core agent](https://github.com/SkyAPM/SkyAPM-dotnet). See .NET Core agent project document for more details.