Installation from live desktop

good morning to all.
I’m just using CL. And I have a little problem.
If I download from Index of /image/ the ISO 39050 and create boot from USB the installation hangs on “download required packs”. if I install the 37980 the installation proceeds but then with the upgrade will generate a flood of errors. In fact in Index of /current/ I can’t find the files that the upgrade is looking for.
Can someone help me?