after a long research I was finally able to get a professional test kit directly from the US to here in Europe.
I've got a taylor service complete kit K2005C in order to perform DPD Clorine (free/combined/total), DPD Bromine (that I do not use at all but are indeed the same CL reagents), PH with Acid and base demand, TA, CH and CYA.
My vinyl swimming pool is actully closed for the winter (meshed cover), only the pump run for about 1 hour/day and I just periodically check Cl and PH with my previous basic test kit.
Today I've run the 1st complete water test and those are the results:
FC = 1
TC = 1
CC = 0
PH = 7,2
CH = 180
TA = 30
I've repeated the TA test twice in order to be sure about the result, as it looks pretty low.
I've put those values in the pool calculator who evaluated a CSI of -1,26 and wondering if withi this value I may got damages in my pool.
Thanks for your help!