Customize a spreadsheet for my yoga class attendance and class package purchases

Hello - I want to create a spreadsheet (Excel, Numbers or Google Sheets) or a Google Form that will allow me to quickly record my yoga class attendance and class pass sales and uses that I can track from my phone. I teach 2 groups of students - one M, W, F, and the other Tu, Th, Sat. Usually there's no overlap in the student population but sometimes there is. Some students are year-round, the others seasonal, so I need to keep track of the last time someone was there - even if it was 6 months prior - and know how many classes are left on their pass. The vast majority buy 10-, 20- or unlimited class passes with me but there are walk-in students too. Basically, I'm trying to replace the paper system in the photo by typing into my iPhone. The pink cards correspond to each student, the white paper tracks one - three classes per sheet. I have 2 classes that recur 3x/week, and a database of about 30 people. Thanks, Jane