Thank you for the answer, that is not easy for me to figure out the various thread systems!
Now there is a machine I might be able to get, a Pfaff 545-H3-6/01-CSMN-8. Searching on the internet, there are some with CLPMN, so the CSMN means C -- for heavy material, S -- for fabrics, am I right? The machine is with MAJER 5000 F3 HP0.5 W370 moter, is this the right type of moter if I want to sew slow?