My last GF had sex with other men. I knew it. I didn’t care. Same as you, when we were together, it was just us. I knew she was careful with who she chose. I didn’t want to hear the details, but I was fine when she mentioned it off-handedly after the fact. It was no more concerning than if she’d told me she’d been to the dentist, or went shopping for a new coffee maker. What she did when I wasn’t around was irrelevant to “us”.
When I was a teen, with my first GF, it was too easy to become jealous.
Over time, and with more experience, I got over myself more after each relationship. By the time I was married, and in the end she had cheated on me, I was sad about losing her and what I thought our life was going to be, but the actual sex with another man didn’t bother me. Then, with my last GF, all that mattered was the time when we were together. What she did in her “free time” was her thing. I didn’t need to control her, I didn’t even want to control her in any way. Love is choosing to be with someone, love isn’t choosing NOT to be with someone else. The sooner people figure that out, the easier life is.
In the mid-70s, in middle school (8th grade), we were taught all about the holocaust-which I remember because of the pictures and movies. I don’t remember what we were taught about the war itself, I’m sure it was covered. I didn’t realize it then, but many of my teachers grew up during, or were adults during WWII, simply based on how old they were. My English teacher that year was 70+, and he told combat stories in class.