Newbie Concerns

I live in China, maybe I'll go back to the USA soon if I feel that I'm not getting good treatment. I had high BP and a rapid pulse. One day, I got very dizzy, I knew from the the feeling that my BP must have run up very high. The school where I worked has a Dr on staff due to Covid requirements. I went to see her and she took me to the ER. I had an EKG and was referred to a cardiologist. I went and at first they thought that I needed a stent. That was delayed because of the pandemic and overcrowded hospital. I was in the hospital for a week of testing; no stent, that's when the HF diagnosis came. On the first echo at the start of this, my EF was 48. On the day that I was discharged from the hospital it was 51. Then 3 months later back down to 48.... I need to know a few things.... Does EF fluctuate? Can it bounce up a few points and go back down? It was 51 in the morning, after a few days resting in the hospital. The test the showed 48 was late in the afternoon, after being active all day... When I go for another echo, is there a time of day that is a better reflection of real health?... If my pulse and BP are well-maintained, should I not sweat the EF, and assume that it's not declining? How often should I get the EF checked?... It seems that, in the big picture of things, at an EF of 48, I'm in the very earliest stages. I'm on Entresto and Bisoprolol