I think as other comments have said, the mixing is a little rough throughout the OST. The use of stock plugins on FL studio mobile I'm sure is to blame but it does negatively affect the OST as a whole.
Don't take that to mean you did poorly. You said this was for practice and I like how much variety there is in the OST. Having a bunch of different tempos and energies is great for engagement and the tracks don't overstay their welcome by being good lengths.