update crosschain migration (#1293)

Author: Celia18305

tutorials/en-us/migration.md

@@ -4,7 +4,7 @@ This tutorial is intended to guide developers in migrating the global assets NEO
 
 ## Exchange to nNEO / cGAS
 
-Since it is not possible to transfer the UTXO asset NEO /GAS into smart contracts, we need to exchange them to nNEO / cGAS which are NEP-17 contract mapping assets, allowing the invocation of funds across chains, precision calculation of assets, as well as interaction with smart contracts. 
+In order to facilitate the invocation and precision calculation of assets across chains, as well as the interaction with smart contracts, we need to exchange the UTXO asset NEO /GAS to nNEO / cGAS which are NEP-5 contract mapping assets and can be divided. 
 
 nNEO and cGAS are open source and can be found in GitHub: [nNEO ](https://github.com/neo-ngd/CNEO-Contract "nNEO") and [cGAS](https://github.com/neo-ngd/CGAS-Contract "cGAS").
 

tutorials/zh-cn/migration.md

@@ -4,7 +4,7 @@
 
 ## 转换 nNEO 和 cGAS
 
-由于智能合约无法调用 UTXO 资产 NEO 和GAS，我们需要将其分别转换成 NEP-17合约映射资产 nNEO 和 cGAS，从而使得资产能被跨链调用，计算精度以及与智能合约进行交互。
+我们需要将 UTXO 资产 NEO 和 GAS 分别转换成 NEP-5 合约映射资产 nNEO 和 cGAS，从而使得资产可分，便于被跨链调用，计算精度以及与智能合约进行交互。
 
 nNEO 和 cGAS 是开源的，可以在GitHub上查看其合约源代码和详解：[nNEO ](https://github.com/neo-ngd/CNEO-Contract "nNEO")和 [cGAS](https://github.com/neo-ngd/CGAS-Contract "cGAS")。