The most complicated thing in America, tax. I'm mostly concerned with income tax because of my paycheck and investment capital gain tax. This is a very hard topic to break into and it took me a long time to find a way to approach this tax topic. I finally found the breakthrough from the paycheck calculator.
Basically just go to any paycheck calculator: https://smartasset.com/taxes/paycheck-calculator
And try to replicate it in Excel or Google Sheet: https://docs.google.com/spreadsheets/d/1f05sqe2_Gy2qo_R1WC42pH0XXcBtP6O1bHBGedSpDl8/edit?usp=sharing
After doing this exercise, I got a deeper understanding of the tax law on income tax. I also got more familiar of reading the tax code on IRS website or reading forum on TurboTax. Oh, talking about TurboTax, I filed my tax on its free alternative, FreeTaxUSA. The experience was very good overall, highly recommend it.