Its because the card is formatted as a Fat32 so it can only record the smaller files. This is very common on other cameras. They all should stitch up seamlessly in any video editor.
I do all my editing on my PC which is Win 10. There are some good free editors such as DaVinci Resolve. There is a learning curve with any editor so Youtube is your friend for learning from the many tutorials people post.
I have been using Wondershare Filmora9 lately and find it very good but it is not free but does offer some great features. If its in your price range I strongly recommend it. As for Android and doing it on your phone or tablet maybe some one else can suggest something for you.
I think filmora 9 is a really good software to do it. Not free, but not really expensive. I paid for it, after try others options, and my impressions can't be better
With a little learn and work, you can obtain really impressive results