Opening almost reminds me of ME1 music. I would take a bit more care with your lower intervals. Octaves and 5ths sound clean in lower ranges than major 3rds, 4ths, and other intervals, which are better separated from your bass instruments. Recommend studying this concept, as it will massively improve your soundscaping ability.
In short, a lot of your interval clashes can be solved by either choosing to omit doubled thirds or fifths of a chord (most people will not double 5ths anyway because they're so strong) or use chord inversions. If you don't know a lot of these terms, I recommend you study music theory. There are plenty of YouTube tutorials for this, and it's fairly easy to understand and implement right away in your music if you're willing to just take a few minutes a day, write notes, and go back to practice some concepts. Seriously, it makes all the difference; take time to learn all the rules so you can later break them.
This piece actually does not sound as bad as you probably think it does. Other than really muddy low end occasionally pumping out, mid range counter melody sticking out a bit over the top of other instruments, and chunky low-mids, this piece is actually atmospherically sound. 3:17 it does start to overdrive and get into distortion territory. Watch your levels and try not to just rely on compressors and brick wall limiting to keep your headroom under control. Definitely recommend mixing and mastering tutorial study there.
Thanks for coming out to NGUAC!