Cleerly get the char render off the s/s. Like seperate the char os i ts a render and not cut like have the body out.

pentool, polygon-, lassotool, erase tool

screw the lassotool.

you can take large portions out of the background with the quick selection tool, just set the tolerace higher like 35+ but make sure you don't clip out the character, if you do its a simple fix.
let me know if you need any more help