How to upload a slow motion video taken on an Honor 7?

[AC Question]

Hello. I can record a video in slow motion fine, and its definitely in slow motion on my phone but how come when ever I try to upload it to facebook or Instagram or send it as a message in WhatsApp or messenger etc. it always plays in normal speed? my last phone I had which was also an android the moto g once the video was recorded in slow motion in uploaded in slow motion. simple. how do you make an Honor 7 do it? ive seen videos on youtube of people uploading a slow motion video on an honor 7 but they offer no explanation as to how its done.