Order Summary Component using mobile first approach

My last submitted project was since a couple of months back...I haven't gotten the chance to code since then.. It feels great doing something like this even though I know there are a lot of errors.. I particularly had issues attempting the mobile first approach for my first time and it came with its own difficulties and complexities...I would be grateful to get a detailed assessment of this mini project and design principles I should take into consideration when coding subsequent projects..Thanks in anticipation!!