hi there :3
can I ask you something? how do you draw the background? do you have everything on one layer? If you have the character and the background on two different layers, how do you manage that they don't overlap?
thx :3
Sure
My layering for this drawing goes like this from top to bottom:
accesories (jewelry, flower)
hair
clothing beige
clothing red
Skin
background lines
background
They don't overlap because each layer stays on top of each other so for example if the hair pin is on top then i can draw the hair underneath it on a separate layer without messing with the accessory. That will always stay on top untouched.
I lock the opacity for each layer and so i can shade them without changing their shape.
This is a basic technique
of how to use layers in photoshop. This technique applies to Paint Tool Sai as well as Corel Painter and judging by your question you are not familiar with it. I hope this explains better how to use layers to freely add background and characters on layers without fear of overlaping 
My layering for this drawing goes like this from top to bottom:
accesories (jewelry, flower)
hair
clothing beige
clothing red
Skin
background lines
background
They don't overlap because each layer stays on top of each other so for example if the hair pin is on top then i can draw the hair underneath it on a separate layer without messing with the accessory. That will always stay on top untouched.
I lock the opacity for each layer and so i can shade them without changing their shape.
This is a basic technique
of how to use layers in photoshop. This technique applies to Paint Tool Sai as well as Corel Painter and judging by your question you are not familiar with it. I hope this explains better how to use layers to freely add background and characters on layers without fear of overlaping OMG!! Thank you soo soo much for your help and your quick respond!! Yes, you really made me open my eyes! It's funny that I didn't know that after using Sai and Photoshop for so many years xDD Kinda embarrassing hahaha
You're welcome dear 