No, it's not natural. In your example, you'd use a word like 'understand' instead of 'digest'.
'digest' has broader use in more formal writing as in journals. But in conversation, the usage is far narrower. Usually it's reserved for when you are talking about meals or food. An example: "I ate too much at lunch and my stomach's having a bit of trouble digesting it". Yes, you *can* use digest a little broader in conversation in some instances ...'He had trouble digesting the news', etc. But not many people will say it this way, so it's very uncommon to hear it.