It’s all Greek to me
Definition 1 of 1
Pro Tip 1/3Figurative Expression
Used when something is too complex to comprehend, not just foreign languages. 
She tried explaining chess strategy, but it’s all Greek to me.
Pro Tip 2/3Informal Usage
It’s a casual idiom, suitable for informal conversations rather than formal or academic writing. 
Can you explain this tax form? It’s all Greek to me.
Pro Tip 3/3Cultural Nuance
Recognize this phrase originates from English-speaking cultures, so it may not resonate in non-English contexts. 
When I used 'it’s all Greek to me' in France, they didn’t understand the expression.