There's not a spell that would immediately implant the knowledge, experience, and use of a language into your mind so that you could suddenly know French, German, Mandarin, etc.; though there are rare medical cases where someone suddenly starts speaking them. Perhaps that'd be something to research for you later.
However, you may request the aid of a deity, after building up a relationship through offerings and gifts, over a period of time before requesting a favor. Deities such as Anubis, Hermes, Nabu, etc. Every culture has a deity for knowledge or language. Pick the one you're comfortable with.
If you are more inclined to put for the effort of learning a language yourself, then you might look towards a spell which aids in the retention of learning and clarity of knowledge. Such a spell would ideally be repeated a few times a day or week so that it becomes more of a mantra that is constantly subconsciously at work taking what you've learned and helping it take root faster in your mind.
The later is more than likely your best option if you haven't been able to see or hear entities before now.