Elastic Search ( opensearch backend) Plugin is not searching partial text

I have found that search is very basic and is not even searching "cloud" from multiple questions having "NextCloud" in title and body .
It is very poor search even in Answer and since opensearch is deployed it should be far better and should be capable of searchings Synonyms. Am I doing some mistake in configuration , how to improve search .
I do not see much options in ElasticSearch Plugin to tune any searching.