About the dissonance - just because all the notes are in the key of E minor does not mean that they don't clash. If you played random notes from any scale, there's a pretty high chance that they would clash horribly. You need to know which notes of the scale to use together and when.
Hey, Epic. Something you need to do - learn some basic music tips. Learn what notes go together and listen to notes that sound good together. This will help you to make awesome melody lines, decoration and add a good bassline to almost any tracks. Any good track will have notes that work together.
This track has a lot of clashing notes (too much for my liking) but the notes are occasionally particularly consonant. Try to stick to consonant notes for now.