doc: refine doc structure and description

docs/en/05-develop/index.md

 ---
+sidebar_label: Developer Guide
 title: Developer Guide
+description: The most fundamental knowledge about programming with TDengine.
 ---
 
 To develop an application to process time-series data using TDengine, we recommend taking the following steps:
@@ -13,7 +15,7 @@ To develop an application to process time-series data using TDengine, we recomme
 7. In many use cases (such as fleet management), the application needs to obtain the latest status of each data collection point. It is recommended that you use the cache function of TDengine instead of deploying Redis separately.
 8. If you find that the SQL functions of TDengine cannot meet your requirements, then you can use user-defined functions to solve the problem.
 
-This section is organized in the order described above. For ease of understanding, TDengine provides sample code for each supported programming language for each function. If you want to learn more about the use of SQL, please read the [SQL manual](/taos-sql/). For a more in-depth understanding of the use of each connector, please read the [Connector Reference Guide](/reference/connector/). If you also want to integrate TDengine with third-party systems, such as Grafana, please refer to the [third-party tools](/third-party/).
+This section is organized in the order described above. For ease of understanding, TDengine provides sample code for each supported programming language for each function. If you want to learn more about the use of SQL, please read the [SQL manual](../taos-sql/). For a more in-depth understanding of the use of each connector, please read the [Connector Reference Guide](../connector/). For more ways to writing data into TDengine, please refer to [Data In](../data-in), for more ways to read data out of TDengine, please refer to [Data Out](../data-out).
 
 If you encounter any problems during the development process, please click ["Submit an issue"](https://github.com/taosdata/TDengine/issues/new/choose) at the bottom of each page and submit it on GitHub right away.
 

docs/en/05-develop/03-insert-data.md → docs/en/08-data-in/01-insert-data.md

+---
+sidebar_label: SQL
+title: Insert Data Using SQL
+description: This section describes how to insert data using TDengine SQL
+---
+
 # Insert Data
 
 import Tabs from '@theme/Tabs';

docs/en/08-data-in/02-prometheus.md

 ---
 sidebar_label: Prometheus
 title: Prometheus for TDengine Cloud
+description: This topic introduces how to write data into TDengine from Prometheus.
 ---
 
 Prometheus is a widespread open-source monitoring and alerting system. Prometheus joined the Cloud Native Computing Foundation (CNCF) in 2016 as the second incubated project after Kubernetes, which has a very active developer and user community.

docs/en/08-data-in/03-telegraf.md

 ---
 sidebar_label: Telegraf
 title: Telegraf for TDengine Cloud
+description: This section explains how to write data into TDengine from telegraf.
 ---
 
 Telegraf is an open-source, metrics collection software. Telegraf can collect the operation information of various components without having to write any scripts to collect regularly, reducing the difficulty of data acquisition.

docs/en/08-data-in/index.md

 ---
 sidebar_label: Data In
 title: Write Data Into TDengine Cloud Service
+description: A number of ways for writing data into TDengine.
 ---
 
-This chapter introduces a number of ways which can be used to write data into TDengine, users can use 3rd party tools, like telegraf and prometheus, to write data into TDengine cloud service, or use [taosBenchmark](../tools/taosbenchmark) which is a tool provided by TDengine to write data into TDengine cloud service. Furthermode, users can use taosX, which is also a tool provided by TDengine, to sync data from one TDengine cloud service to another.
+This chapter introduces a number of ways which can be used to write data into TDengine, users can use 3rd party tools, like telegraf and prometheus, to write data into TDengine cloud service, or use [taosBenchmark](../tools/taosbenchmark) which is a tool provided by TDengine to write data into TDengine cloud service. Users can use taosX, which is also a tool provided by TDengine, to sync data from one TDengine cloud service to another. Furthermore, 3rd party tools, like telegraf and prometheus, can also be used to write data into TDengine.
\ No newline at end of file

docs/en/05-develop/04-query-data.md → docs/en/09-data-out/01-query.data.md

+---
+sidebar_label: SQL
+title: Query Data Using SQL
+description: This topic introduces how to read data from TDengine using basic SQL.
+---
+
 # Query Data
 
 import Tabs from '@theme/Tabs';

docs/en/09-data-out/03-taosdump.md → docs/en/09-data-out/04-taosdump.md

+---
+sidebar_label: taosDump
+title: Dump Data Using taosDump
+description: Introduces how to dump data from TDengine into files using taosDump
+---
+
 # taosDump
 
 taosdump is a tool that supports backing up data from a running TDengine cluster and restoring the backed up data to the same, or another running TDengine cluster.

docs/en/09-data-out/index.md

 ---
 sidebar_label: Data Out
 title: Get Data Out of TDengine
+description: A number of ways getting data out of TDengine.
 ---
 
 This chapter introduces how to get data out of TDengine cloud service. Besides normal query using SQL, users can use data subscription which is provided by the message queue component inside TDengine to access the data stored in TDengine. `taosdump`, which is a tool provided by TDengine, can be used to dump the data stored in TDengine cloud service into files. `taosX`, which is another tool provided by TDengine, can be used to sync up the data in one TDengine cloud service into another.
\ No newline at end of file

docs/en/10-visual/index.md

 ---
 sidebar_label: Visualization
 sidebar_title: Visualization
+description: View TDengine in visual ways.
 ---
 
 This chapter introduce some visual ways to view TDengine, either its running status or the data stored in it. More and more visual ways will be coming.
\ No newline at end of file

docs/en/12-taos-sql/index.md

 ---
-title: TDengine SQL
-description: "The syntax supported by TDengine SQL "
+sidebar_label: SQL Reference
+title: TDengine SQL Reference
+description: Full reference manual of TDengine SQL.
 ---
 
 This section explains the syntax of SQL to perform operations on databases, tables and STables, insert data, select data and use functions. We also provide some tips that can be used in TDengine SQL. If you have previous experience with SQL this section will be fairly easy to understand. If you do not have previous experience with SQL, you'll come to appreciate the simplicity and power of SQL. TDengine SQL has been enhanced in version 3.0, and the query engine has been rearchitected. For information about how TDengine SQL has changed, see [Changes in TDengine 3.0](../taos-sql/changes).

docs/en/17-tools/index.md

-#  Tools
+---
\ No newline at end of file
+sidebar_label: Tools
+title: Tools
+description: Useful tools provided by TDengine
+---
+
+In this chapter, the most useful tools provided by TDengine are described in details for users to use TDengine more smoothly.
\ No newline at end of file