What should I do if I don't know how to finish these challenges

Hello, everyone, I’m a newbie here. I didn’t know anything about code programming before. Right now, I’m learning the Kotlin language book, chapter 4, Functions. And I find it is hard for me to finish these challenges. I understand some concepts, but I am not capable of using them, such as syntax, when/if functions etc. What should I do? Should I put them aside?