First time to edit you are going to include a lot of what should really be removed, take this same set of video files and work them again, then do it again, and maybe even a few more times and you will find improvements with each round of edits, it's a learning process.
Others have mentioned, the transitions you used need to go, I am sure you have watched TV and movies, and you really find only 3 transitions used in the majority of work you see that makes it to the big screen.
With the most common. the cross fade, where one scene and the next fade from one into the other, and it's especially useful when the going from one scene to the next has the ability to "morph" in a way that makes you go WOW.
The straight cut from one scene to the next is used even more than the cross fade, but we as viewers don't even think of it as a "transition".
The third, yet to be used very sparingly, is the fade to black, but use it only when the subject matter, makes a change to a different subject matter in most cases, so it would pretty much not be used in something like this group of files that is a flowing story of two bikers in the beautiful green foothills.
So yes, transitions is a big error in this first edit, but by far not your major error.
Your major error is to include "footage" (going back to the days of film), that is not interesting, or causes your head to spin. When the camera movement is too much where they riders go out of scene, edit out "footage" and cross fade or straight into the next good segment of footage.
Edit out all footage that is not interesting, you have spots in this were it takes a number of seconds before their is any action of any kind, especially right at the beginning.
Do understand a second or two of smooth moving flight can be interesting even if no biker is in the scene if you pick the right footage.
Your 5 minute video if edited well, should maybe less then a minute long if it should even should be that long.
Not trying to say it was a bad first edit, just trying to help you see that now that the "first edit" is behind you, and you have the files to work on it again, and again to get it right, so don't stop, and don't just wait to edit the next group of files you want to use, to take these same files and turn it into a 30 second commercial for the promotion for riding a motocross bike in the green hills in spring.
Once you take on group of files and work on them to the point of having that eye grabbing 30 seconds, you will start to see in future projects that you will get there sooner in making something that will grab the interest of the viewer.
I hope my thoughts here help you or any of the other readers.