keyboard – Remapping Mac keys

I just bought a KeyChron K4 keyboard (Gateron Blue switches – it's great) and the layout is a little different from the 104 standard keys.

I want to exchange two keys – the problem is with Karbiner if I change a key for the other function (num / clear for a small del key), when I then try to change the del key (original) for the new num / clair, it actually changes the key del that I just created.

I watched Ukulele (I actually installed it), but it sounds too complicated for me. Is there an easy to understand tutorial?

Is the BetterTouch tool easier to use and will it do what I want? Thank you.