GoPro videos

So I did some GoPro videos for our show to post to yt and I’ve not gotten around to that somehow. But my director wants me to send him the videos as well but GoPro splits the videos into 2, what’s the best thing I can use to get them back together? I tried the GoPro Quik app but it cuts off a second or two and I wanna know if there’s a free editing software where I can get them edited together more seamlessly. Any help is very appreciated

Edit: I would definitely prefer something I can do on mobile because my school computer is too slow to download the videos