Hey @Ricardo_Damborenea, it looks like your Mac Mini doesn’t meet the minimum requirements for the Roon Core (you need at least an Intel Core i3, Ivy Bridge or later). This will be especially apparent with a library as large as yours, and what you’re experiencing sounds like expected behavior.
If you’re looking for an appliance that can manage 140k tracks, I’d recommend considering a Nucleus Plus.
For what it’s worth, I have the same vintage of Mac Mini and I don’t have those same issues. However, my library is significantly smaller than yours. It may be that your system doesn’t have enough puff for a database of that size.
Assuming you purchased from an apple retail outlet of apple online then you have 2 weeks to return it no questions asked and could order a 16gb unit. 256G for the os and roon is ample assuming no local library on the same machine.