Welcome to Android Central! MMS (i.e., sending photos or videos via text messaging) has a filesize limit of around 1 MB. Most videos are much bigger than this, and no degree of compression will make them sendable via MMS. Your best bet is to upload the video somewhere like YouTube or your Google Drive or Google Photos, and share the link privately with the recipient. This is essentially what happens if you send a video file to someone via Google Hangouts instant messaging--your video gets uploaded to your Google Photos, and the link is shared privately with the recipient. Only you two can see it--it's not posted to Google for the entire world to see.