Like Callenby said, the entire thing sounds like almost exactly like Pachelbel's Kanon; I can't really blame you for doing this as it looks like you're fairly new, and when I was just starting out I did the same thing. But if you're looking into developing your own composition style, run as far away from that song in particular as you can. Yes, its very popular; yes, it sounds good; yes, everyone knows it; its a very very easy song to identify. Its chord progression is nearly as old as sheet music itself, and no matter what key or inversion its in, people can usually recognize it. [Its not that great of a song anyway, and its a terrible kanon (actually its fairly okay but its weird and there's a reason it stands out)]
Anyway, the song itself (getting away from what it came from) is really repetitive. Helpfully enough, there is currently a semi-active topic that is meant to go over how to fix all the problems with repetitiveness in orchestral music and making it more interesting for both the listener and the composer.
viewtopic.php?f=32&t=8691Also, you really need to work on your song continuity. Like Callen said, the transitions were jarring. Here are a few ways to fix it:
1. Make sure you bar lines "loop": Kanons (and music in general) is composed in blocks, usually of two/four/eight sections of four closely related measures. To keep a flow, make sure the last measure and the first measure can flow into each-other AKA, make sure the last note of the section is a semi/whole tone away from the first note, or have it be a perfect interval that resolves. When this is done, you should be able to press "Play Loop" button on your DAW and hear no gap or awkward pause when the loops.
2. Rhythmic Changes: If you plan on going from a moderately sped section (A) to a rapid one (B), make sure that you either:
a) Gradually build into it by employing faster notes in the bass-line and melody; which creates a smoother change and is can go unnoticed, but don't do it more than one time in a row; it can get tedious.
b) Make a sudden change by writing longer notes in A than the rest of the section, which builds tension using differences in pacing. The franticness of B can release this (in most other genre's this would be called a drop), this type will be strongly noticed, and can be done multiple times, but you have to remember that if you drop, you have to get up again.
Overall, orchestral composition takes a lot of time to do well, but can be very useful; so try just listening to more classical music (of all time periods), look at the scores, analyse the chord progressions and voicing, and generally just practice more.