You can use a video compressor to shrink it’s by by reducing the bitrate, frame rate, resolution and changing the codec.
In my experience, if you don’t have to play the video with a ultra high resolution devices, then it should be completely acceptable to downscale 4K to HD, saving 3/4 of the size. The proper frame rate and bitrate value depends on the content of your video. Re-encoding the file to HEVC also helps a lot.