The strange thing with the website speed

Every now and then I check the speed of my various websites with Google https://developers.google.com/.... At the beginning I was happy, all seemed to be really good, green was the constant color.

Then I didn't check for a while and when I did it again everything was dark red. Then you still got the calculation also for mobile - or is this check for mobile? I have no idea at this pont as it says "unavailable" - and it was far worse than on desktop. I didn't know what to do. There were indications to optimise certain pictures, but the ones they named were not in my library. I asked the theme support and they said that they were inherent to the theme and that I couldn't do anything. Well - ???

Then there was something about javascript. Although I now know what that means I had no idea what they were suggesting that I should do, and even less HOW. I again asked support, but that didn't bring me further. So I just let it go, I felt helpless and hoped for better times. I hadn't understood why it had become so much worse, and so, who knows, it could get better in the same ways.

And actually, it did. When I checked lately I was first yellow, and only one hour later even in green. Yeah! Happy again, but no idea what had caused it. I hadn't changed anything essential, only added some more pages and posts in the same way as ever.

Then, the next day

I checked again - and no green at all, down to yellow, but at least not red, as it was some time before.

I am not aware to have changed anything to cause that and I am very curious if anybody knows how these results come out? It doesn't seem to be a reliable information. And also I wouldn't know what to do to keep the speed in "green". Do YOU? If you do, please let me know.

All the best from Heidi in Italy - working hard in trying to understand all this website stuff...