Based on research, is it better to learn a new language in your mother tongue?

I live in a multilingual country and often people that visit a language course will have the class in one of the languages spoken here, let’s say French.
But most of these people do not speak a lot of French and there are a lot of problems that arise because some sound does not exist in their mother tongue or the grammar is just different and those problems do not exist in French.

Do you know if there has been any research about learning a language in a course adapted to your mother tongue vs. in a secondary language?