Unit 5 traversals - help!

I am finding the lessons on traversals quite confusing for me (unit 5 lessons 9-12). I’m a trained math teacher and am in my 2nd year teaching APCS so I’m also learning while I’m going. I’m finding myself stuck/confused a bit on the traversals, which makes me concerned because I have to teach it to my kids in 2 weeks, and I might not be able to help them troubleshoot to the level that I normally do. Any tips and or hints for that subunit would be greatly appreciated from a more experienced CS teacher!
With that in mind, I’m stuck on unit 5 lesson 11, activity #8. The other activities were really just copying what was done earlier in on the code. Here is what I did so far, and the average button didn’t work.

Here is my app so far: https://studio.code.org/projects/applab/gwfdjq8O1eznZlg94PwQjSLu2eDDjSJhdy_Zzs3tDKU

I ran it and it seems to be running ok - I’m guessing you figured it out?