Geeetech A30 Conversion (hotend, linear guides/rails (MGN12H))

My printer started missing layers I thought. Finally nothing came out of the nozzle anymore. After a lot of digging I found that the hotend was completely filled up with filament because there seemed to be a leak betweend PTFE tube and nozzle. I finally found this design https://www.thingiverse.com/thing:3237827 and ordered a XBR-BP6 hotend which leads the PTFE tube down to the nozzle.
While disassembling my printer I decided to change X and Y to linear guides/rails and so had to design a moun