Instagram have set a limit on the duration of the videos on Instagram.
If you want to post a video on Instagram, you can post maximum 60 seconds of the video. Your video is long, then you have to cut it and make the duration of 60 seconds. You can post multiple videos which can help you post complete video but at one time, 60 seconds is the limit.
If you want to post a video in Instagram stories, then you can post maximum 15 seconds of the video. You can trim the video in third party app and can make it 15 seconds.