If I want to make a card game app or android, could I legally borrow parts of the Apache-2.0-licensed Solitaire-for-Android? Would I be able to charge such a project? (I was unable to understand the legal jargon in the license here.)
It's actually a very simple license, worth reading with due respect. If you can ask the question in English, I'm very sure you can comprehend the license - just try once again, without distractions.
In short, you can (section 3) IF you follow the rules (section 4 through 9). If you don't follow, then you are in violation.
Disclaimer: I'm not a lawyer and in your shoes, I'd get a legal opinion instead of a random dude online.