Learn Italian: Anche se sbaglio, imparo da ciò che faccio. - Even if I make a mistake, I learn from what I do.

Chi is used strictly for people (meaning "he who", "whoever", or "the people who"). Since this sentence is about an action or a concept ("what I do"), you must use ciò che (literally "that which"). If you said imparo da chi faccio, it wouldn't make sense because it would mean "I learn from the person I do".

Could I use quello che instead of ciò che in this sentence?

Yes! Ciò che and quello che mean exactly the same thing ("that which" or "what"). Quello che is very common in everyday spoken Italian, while ciò che sounds just a little bit more formal or written, but both are perfectly correct here.

Why is "I make a mistake" translated just as sbaglio?

In English, we use the phrase "make a mistake," but Italian has a single verb for this: sbagliare (to make a mistake, or to be wrong). Sbaglio simply means "I make a mistake" or "I am wrong." You never use the verb fare (to do/make) to translate this phrase.

I've heard that anche se (even if) sometimes triggers the subjunctive mood. Why is sbaglio in the normal present tense (indicative) here?