If your device is compatible with HEVC/x265 video (significantly reduced file size compared to the more widely compatible x264, if your pc can't play x265 videos I think there's a HEVC codec you can download on the Windows store) and you know how to use ffmpeg (if not, look up a tutorial on how to install it and how bat files work), this is the ffmpeg line I use to drastically reduce the size of pretty much all mp4s.
for %%f in (*.mp4) do ffmpeg -i %%f -shortest -vcodec libx265 -crf 22 "%%f.mp4"
Make sure you remove all special characters/spaces in the file names before running them through that. 22 is the highest crf I usually set it to; you can set it higher but I noticed that for a lot of media, I start noticing the decrease in quality at about that. For Somato's videos, it generally results in a bitrate of about 5k~. 28 is viewable if you're really down bad for space and are fine with a somewhat noticeable quality drop.