When I pay more of 9% Class 4 NI, does it mean I will get more pension to my retirement pension as it accumulates? Or it doesn't make any difference to my future pension?
Class 4 NI doesn't get you anything (other than avoiding the trouble you might be in for not paying it!).
If you're paying Class 4 then presumably you're also paying Class 2? Class 2 does count towards amassing qualifying years which go into calculating how much state pension you may be entitled to.