sevastase,
I notice you get a lot of hate around here. Some of it's deserved but most of it isn't. Honestly like others have said you have a good build for a natural lifter and it's good to see you're trying to bring up your weaknesses. The only adivce I can give you is to keep with it, partial reps = partial development, control, and eat as much protein as possible.
I too once had a lagging chest and it depressed me. I thought I could bench a shit load of weight and get a big chest like Ronnie, but it didn't work. I went back to basics (full ROM) and brought up my protein intake and it's no longer lagging.