I see. Well this is a huge field. To learn what you just described might take hundreds of hours, even thousands. But I can try to assist you a little bit.
Real instruments are harder to mix than midi stuff for sure.
I developed my ear for years, making hearing training and stuff like that.
I will listen to your EP, since I don´t know the level you are on at the moment.
It´s always a good start point and important to know how to read the frequency spectrum. Get an analyzer for sure to always look at it and learn reading it. This will help you.
What software do you use?
I have ableton because it’s what friends used when I was in the studio with them so I already understood some of the very basics. Then I found a focusrite set that came with ableton
Ah yeah that´s good, if someone is showing it to you. Nice. I had focusrite before.