Bonjour 
You need probably to define your own analyzer. I'd use some ngrams, lowercase and asciifolding token filters.
If you can't make it work, could you provide a full recreation script as described in About the Elasticsearch category. It will help to better understand what you are doing. Please, try to keep the example as simple as possible.
A full reproduction script will help readers to understand, reproduce and if needed fix your problem. It will also most likely help to get a faster answer.
In case you need, there's also a french speaking space: #in-your-native-tongue:discussions-en-francais