I'd like to know how to convert an indicator from mql4 to mql5 AND the language of MQL5 .
For the next time, would you please read as many as you could before posting, there are plenty information about this already in mql5.com.
1. Use mql5 search and type mql4 and you will find this https://www.mql5.com/en/search#!keyword=mql4
2. MQL5 reference is available through MetaEditor 5, just click help and select MQL5 Reference. This is the online version https://www.mql5.com/en/docs
3. Please read this article Migrating from mql4 to mql5
4. This section in mql5 reference explaining about indicator Custom Indicators