repainting help.

Hello everyone, I am needing some help with a repaint. i downloaded both the Ifly 737 repaint kit and the qualitywings 757 paint kit. and first with the ifly, the textures on the main fuselage are merged already and it has the default ifly livery on it so if i paint it i loose all the base textures. as for the qualitywings 757, the main fuselage psd file wont open for me. i use Paint.net and i cannot figure this out. also the textures are blurry when i install them. so if you remember the textures on fs2002 and some on the older planes in fs2004, they are crisp from the side, but as you look closer from the front, they get blurry. Any help would be appreciated. I want to make repaints for these aircraft, but it i cant due to these problems.

airline i want to repaint: Cologne International

https://cologne-international.com/en/