Would someone please check this for me.
Entonces quería que ellos hablaran en su lengua y es bastante complicado buscar traductores,
2 Answers
I'd use idioma instead of lengua, just a personal preference.
Entonces quería que ellos hablaran en su idioma y es bastante complicado buscar traductores.
- su > comes from him, her, you or them?
Por eso quería que ellos hablaran en su lengua propia porque es bastante complicado buscar traductores
What I thought you (now me) were trying to say:
Therefore I wanted them to speak in their native tongues because it is somewhat complicated to find translators.
It is usually advisable to include your English intent so other interpretations don't diverge from what you wanted to say originally.