Question: There is a famous sentence in my language (maybe it exists in other languages too), which is

> 
> what doesn't kill you, makes you stronger
> 
> 
> 

I tried to translate exactly from my language, that is why i used **doesn't**, but i am thinking about it as an English learner. Should it be **didn't** ? because the meaning of the sentence is `what didn't kill you **in the past**,` will make you stronger **in the future**

Answer: 
In English, the phrase is exactly as you've written it. Here's [Kelly Clarkson singing it](https://www.youtube.com/watch?v=Xn676-fLq7I).

My take is that it's referring to thing that make you stronger by not killing you, so both are happening at the same time.
Let's take another contemporary English saying or adage: 

**Karma's a bitch!**

That is, Karma *is* a bitch. Present tense. A typical context for its use is one where the villains in a movie have just received their comeuppance.

Let's make it not a very good movie. The villains are a bunch of bullies who have been stealing the lunch bags of younger kids on their way to school. One of the villains eats a stolen banana, throws the banana peel onto the sidewalk, and then slips and falls on the banana peel. Even though the action of his slipping and falling has already taken place:

Little Kid: Karma's a bitch.

The End