why, like asking the history of the world in a few sentences…
maybe you should start by buying a nice, short history of western music and take it from there . there are so many, the oxford one is great but several volumes, probably too much for starters
also all music is not enjoyable at the same level.
Mozart italian operas as it has been noted are some of the greatest mastepieces ever and readily accessible to anyone
beethoven’squartets are equally great but much more difficult, bach’s WTC and Goldberg very difficult also.
difficult to advice, take it slowly is a big and steep mountain.
I should add that I do envy you. I wish I could hear again some of that music for the first time…