Thanks for sharing your score as a pdf, that's a cool thing to do! :) I like your structure, alternating between pure bell parts and parts where the other instruments kick in is a nice touch.
A few ideas that I think might improve your composition:
- The quality of the MuseScore standard instruments is not very good, which makes sense since it's meant to be a composition and not a music production software. However, an easy way to improve that sound is by installing sound fonts, which make the playback instantly quite a bit more realistic.
- There's a lot of other stuff in music besides the notes themselves. I think your score would benefit a lot from adding some dynamics and articulation (though I know they're a pain to notate, but they do help). Also, your rhythms right now are very basic and adding some rhythmic variety might help a lot.
- Lastly since your interpretation of the theme explicitely focuses on the different instruments, I think it would make sense to always think about what are fitting parts for the instruments and not just write any melody for any instrument. For example, brass instruments often like either playing fanfares or some sort of jazzy stuff. Hand bells really live from harmonies and could probably use more than two parts. Basically, always think about the instrument you're writing for.
Anyway, congratulations on your first submission! Hope you had a blast composing this and you should definitely be proud of yourself!