Why do some of my YouTube videos are either too short or pixelated?

☝️ is a good example of an SD type of video on my channel. And the main reason behind it is my internet connection which doesn't process a YouTube upload over 100Mb (yup, it takes almost an 30 mins for 100Mb from time to time). Due to the lockdown I can't upload high definition videos from office as before, so have to compromise from time to time. Meeeh