Frame and Fork compatibility - 1 1/4" to 1 1/2" I've bought a new frame being this one: https://www.bike-discount.de/en/buy/cube-axial-wls-pro-frame-black-n-green-643919


  Headtube diameter: Tapered 1 1/8" - 1 1/4" semi-integrated ZS44 - full-intgrated IS47  (Cube Headset FSA Orbit Z-t Eco #10359)


I already have a fork from another bike which is 1 1/8" to 1 1/2"

I wonder how can I mount this fork on the frame, since the fork is larger than the bottom part of the frame, I think that something like this could do, but I'm unsure: 


Hope brand - Lower Cup Semi Integrated 1 1/2" black

If that's not going to fit, which options do I have?

Thanks, any help is appreciated!
While there are options for mounting a smaller fork in a larger headtube, they're rare, weird and expensive.

For the opposite - The only way to mount a larger fork steerer in a smaller head tube is swap frame or fork, or replace the steerer on the fork.  Either will have costs.

Sounds like you need to find a fork that will fit your frame. Sorry.